OXDC-ADV-2026-0003
Metadata
- Document type: OX Dovecot Security Advisory
- Publisher: Open-Xchange GmbH
- Classification: TLP:GREEN
- Publication Date: 2026-08-26
- Current version: 4
- Version status: Final
- Aggregate severity: Critical
References
Vulnerabilities
CVE-2026-33263: submission-login: Panic when mail_max_userip_connections is reached: Panic: epoll_ctl(del, 8) failed: Bad file descriptor
- CVE reference: CVE-2026-33263
- Internal reference: DOV-8476
- CWE: CWE-403 (Exposure of File Descriptor to Unintended Control Sphere ('File Descriptor Leak'))
- Discovery date: 2025-11-25
Description
When mail_max_userip_connections is set (default 10) and reached, submission-login can crash with epoll() panic caused by file descriptor handling issues.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
Threats
Impact
If running in high-security mode (default for community releases), only the new submission connection gets terminated. If running in high-performance mode (default for Pro releases), all connections handled by the submission-login process will be terminated. The crashes can cause failure for user to send a message, or it can cause duplicate messages to be sent. If TLS is not used (in the backend server processing the submission), duplicate deliveries cannot happen, because the crash can only happen at AUTH stage.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Limit the number of connections handled by single submission-login process. This has a performance impact though. Update to non-vulnerable version.
CVE-2026-33607: Dovecot IMAP LIST match_sub() Exponential Backtracking — CPU Denial of Service
- CVE reference: CVE-2026-33607
- Internal reference: DOV-8874
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-03-11
- Researcher credits: ylwango613@yeswehack
Description
An attacker that has valid credentials can use IMAP LIST command to consume CPU.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
Threats
Impact
This can cause degradation or denial of service for IMAP.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Monitor system for abnormal CPU usage and kill the offending process and lock account. Alternatively install fixed version.
CVE-2026-27852: DoS by sending mail with bad header
- CVE reference: CVE-2026-27852
- Internal reference: DOV-8884
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-03-13
Description
An attacker that can send mail to a user can craft a message whose headers contain a very large number of email addresses or MIME parameters, which causes excessive memory usage when the message is later parsed.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
Threats
Impact
The message is still delivered, but reading it over IMAP can exhaust the memory limit of the process and terminate it, causing denial of service for the affected user.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Update to non-vulnerable version.
CVE-2026-33606: dsync: Mail content can cause dsync protocol injection
- CVE reference: CVE-2026-33606
- Internal reference: DOV-8941
- CWE: CWE-93 (Improper Neutralization of CRLF Sequences ('CRLF Injection'))
- Discovery date: 2026-03-24
- Researcher credits: thanos_haruki@yeswehack
Description
Mail content stored by a user can be crafted so that it is interpreted as dsync protocol commands when an administrator later runs dsync with the stream protocol, for example during a migration.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:N | 4.8 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:N | 4.8 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:N | 4.8 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:N | 4.8 |
Threats
Impact
Injected commands can modify mailbox state on the destination during migration or replication, including internal mailbox attributes that a user should not be able to set directly. It can also cause dsync errors.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Avoid running dsync with the stream protocol on mailboxes with untrusted content. Update to non-vulnerable version.
CVE-2026-33604: SMTP Smuggling via Missing Dot-Stuffing After Bare Carriage Return
- CVE reference: CVE-2026-33604
- Internal reference: DOV-8947
- CWE: CWE-655 (Insufficient Psychological Acceptability)
- Discovery date: 2026-03-24
- Researcher credits: heckintosh@yeswehack
Description
An attacker that can get Dovecot to relay a message, for example through Sieve redirect or submission relay, can use a crafted line ending in the message body to bypass the outbound protection that prevents message content from being interpreted as SMTP commands.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N | 5.9 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N | 5.9 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N | 5.9 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N | 5.9 |
Threats
Impact
A downstream mail server that hasn't yet fixed the SMTP smuggling vulnerability can be tricked into treating part of the message body as new SMTP commands, allowing injection of spoofed email. This is the same vulnerability class as CVE-2023-51764 and CVE-2023-51766.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Where you control the receiving mail servers, ensure they reject bare carriage returns in message data. Update to non-vulnerable version.
CVE-2026-40014: IMAP THREAD REFERENCES O(N²) CPU DoS via Crafted References Header (index-thread-links.c)
- CVE reference: CVE-2026-40014
- Internal reference: DOV-8949
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-03-24
- Researcher credits: djvirus@yeswehack
Description
An attacker that can send mail to a user can craft a message header that makes the IMAP THREAD command consume CPU disproportionate to the size of the message.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H | 6.5 |
Threats
Impact
When a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version.
CVE-2026-40013: pigeonhole: Stack Buffer Underflow in Pigeonhole ManageSieve CHECKSCRIPT/PUTSCRIPT
- CVE reference: CVE-2026-40013
- Internal reference: DOV-8991
- CWE: CWE-124 (Buffer Underwrite ('Buffer Underflow'))
- Discovery date: 2026-04-02
- Researcher credits: ilyar@yeswehack
Description
An attacker that has valid credentials can submit a Sieve script containing an extreme numeric literal, which causes an out-of-bounds write when the ManageSieve service compiles the script.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
Threats
Impact
This causes memory corruption and an observed crash of the ManageSieve process, resulting in denial of service for script management. This might be able to be used for remote code execution.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Disable the ManageSieve service if users do not need remote Sieve script management. Update to non-vulnerable version.
CVE-2026-33605: managesieve-login: Pre-auth crash
- CVE reference: CVE-2026-33605
- Internal reference: DOV-8994
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-04-02
- Researcher credits: ilyar@yeswehack
Description
An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
Threats
Impact
If running in high-security mode (default for community releases), only the attacker's own connection is terminated. If running in high-performance mode (default for Pro releases), all connections handled by the same managesieve-login process are terminated. Repeating the attack can cause denial of service for Sieve script management.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable version.
CVE-2026-40018: MySQL multi-byte escaping wrong
- CVE reference: CVE-2026-40018
- Internal reference: DOV-9039
- CWE: CWE-89 (Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection'))
- Discovery date: 2026-04-08
- Researcher credits: tipsennn@yeswehack
Description
None
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <3.1.6 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N | 7.4 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N | 7.4 |
Threats
Impact
None
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
None
CVE-2026-40019: v2.4.3 regression: managesieve-login pre-auth infinite loop
- CVE reference: CVE-2026-40019
- Internal reference: DOV-9041
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-04-08
- Researcher credits: ilyar@yeswehack
Description
An unauthenticated attacker can send a truncated quoted argument to the ManageSieve login process, which makes it spin in an infinite loop consuming CPU.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot CE core >=2.4.3 <2.4.5 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H | 5.9 |
Threats
Impact
This can cause degradation or denial of service for Sieve script management, and repeated connections can consume all available CPU on the server.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot CE core 2.4.5
Monitor system for abnormal CPU usage and kill the offending process. Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable version.
CVE-2026-40015: imap-hibernate can be crashed
- CVE reference: CVE-2026-40015
- Internal reference: DOV-9046
- CWE: CWE-125 (Out-of-bounds Read)
- Discovery date: 2026-04-08
- Researcher credits: tipsennn@yeswehack
Description
An attacker that has valid credentials can open many connections to the imap-hibernate service and send invalid commands, which can intermittently cause an out-of-bounds read and crash the process.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
Threats
Impact
The crash interrupts hibernated IMAP sessions handled by the affected process, which can cause degradation of service for IMAP.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Disable IMAP hibernation. Update to non-vulnerable version.
CVE-2026-40017: IMAP THREAD O(M³) CPU DoS via CRC32 Hash Collision in strmap (mail-index-strmap.c / hash2.c)
- CVE reference: CVE-2026-40017
- Internal reference: DOV-9047
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-04-08
- Researcher credits: djvirus@yeswehack
Description
An attacker that can send mail to a user can craft a message header whose values are chosen to collide in an internal hash table, which makes the IMAP THREAD command consume CPU disproportionate to the size of the message. This is a separate issue from CVE-2026-40014 and is not addressed by that fix.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H | 6.5 |
Threats
Impact
Whenever a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version.
CVE-2026-40203: IMAP Compression Can Reveal Whether a Small Synced Email Body Matches Sender-Chosen Text
- CVE reference: CVE-2026-40203
- Internal reference: DOV-9066
- CWE: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)
- Discovery date: 2026-04-12
- Researcher credits: ilhamaf@yeswehack
Description
When IMAP compression is enabled, the same compression state is reused across responses in a session, so response sizes depend on both attacker-supplied mail and other mail in the same mailbox.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | 3.7 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | 3.7 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | 3.7 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | 3.7 |
Threats
Impact
An attacker that can send mail to a user and can also observe the sizes of that user's IMAP traffic can confirm whether the body of a small message matches a guessed text. Recovery of arbitrary unknown content was not demonstrated, but the attack can disclose whether a secret-like message body matches a candidate.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Disable IMAP compression. Update to non-vulnerable version.
CVE-2026-42007: Sieve editheader RCE
- CVE reference: CVE-2026-42007
- Internal reference: DOV-9070
- CWE: CWE-416 (Use After Free)
- Discovery date: 2026-04-14
- Researcher credits: ilyar@yeswehack
Description
An attacker that has valid credentials can use a Sieve script with the editheader extension to trigger a use-after-free in the mail editing code, and to write memory contents beyond the intended buffer into the delivered mail.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H | 9.1 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H | 9.1 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H | 9.1 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H | 9.1 |
Threats
Impact
This causes memory leak and opportunity to do memory corruption during mail delivery, which can crash the delivery process and may allow execution of arbitrary code in the context of that process.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Disable the Sieve editheader extension. Update to non-vulnerable version.
CVE-2026-40204: acl: lda_mailbox_autocreate can bypass acl restrictions
- CVE reference: CVE-2026-40204
- Internal reference: DOV-9099
- CWE: CWE-284 (Improper Access Control)
- Discovery date: 2026-04-22
- Researcher credits: ilhamaf@yeswehack
Description
None
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N | 3.1 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N | 3.1 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N | 3.1 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N | 3.1 |
Threats
Impact
None
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
None
CVE-2026-40205: OAuth2 passdb scope enforcement bypass via OR semantics in remote validation path
- CVE reference: CVE-2026-40205
- Internal reference: DOV-9106
- CWE: CWE-287 (Improper Authentication)
- Discovery date: 2026-04-23
- Researcher credits: Noobosaurus@yeswehack
Description
An attacker that holds an OAuth2 token granting only part of the required scopes can authenticate, because when more than one scope is required in the configuration, the remote token validation paths accept a token that carries only one of them, while the local token validation path correctly requires all of them.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.11.2 <2.3.22.2 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N | 5.9 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N | 5.9 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N | 5.9 |
| OX Dovecot CE core >=2.3.11.2 <2.4.5 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N | 5.9 |
Threats
Impact
The configured authorization policy is not enforced, so a token that was granted only part of the required permissions is accepted where it should have been rejected.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Use local token validation where tokens can be validated locally. Update to non-vulnerable version.
CVE-2026-42008: XCLIENT FORWARD= bare token not namespaced, allows nopassword injection via trusted proxy
- CVE reference: CVE-2026-42008
- Internal reference: DOV-9109
- CWE: CWE-287 (Improper Authentication)
- Discovery date: 2026-04-23
Description
Forwarding information received from a host listed as a trusted proxy is not kept separate from Dovecot's own authentication fields, so a value sent by that host can be injected as an internal authentication field.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.4 <2.3.22.2 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | 4.3 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | 4.3 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | 4.3 |
| OX Dovecot CE core >=2.3.4 <2.4.5 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | 4.3 |
Threats
Impact
Any host permitted to act as a trusted proxy can authenticate as any user without knowing that user's password. This affects deployments whose password database honours a field that permits authentication without a password. Deployments that do not configure trusted proxies are not affected.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Restrict the list of trusted proxy networks to hosts that are fully under your control. Update to non-vulnerable version.
CVE-2026-42395: Single NUL-Byte XCLIENT FORWARD Payload Crashes
- CVE reference: CVE-2026-42395
- Internal reference: DOV-9142
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-04-27
- Researcher credits: ilhamaf@yeswehack
Description
A host listed as a trusted proxy can send forwarding information containing a NUL byte, which crashes the login process on the following login attempt.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | 4.3 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | 4.3 |
Threats
Impact
The login process is terminated, which can cause degradation or denial of service for logins. Deployments that do not configure trusted proxies are not affected.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Restrict the list of trusted proxy networks to hosts that are fully under your control. Update to non-vulnerable version.
CVE-2026-42393: doveadm_password or api key length can still be leaked with timing comparisons
- CVE reference: CVE-2026-42393
- Internal reference: DOV-9148
- CWE: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)
- Discovery date: 2026-04-27
- Researcher credits: D4RKCYPH3R@yeswehack
Description
The comparison used for the doveadm password and API key is not fully timing safe and can reveal the length of the configured secret.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | 3.1 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | 3.1 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | 3.1 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | 3.1 |
Threats
Impact
An attacker with access to the same network as the doveadm service, able to make repeated requests and measure response timing accurately, can learn the length of the secret, which reduces the effort needed to guess it. The secret value itself is not disclosed.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Restrict network access to the doveadm service to trusted clients. Update to non-vulnerable version.
CVE-2026-52681: Sieve resource usage tracking lost when active script changes
- CVE reference: CVE-2026-52681
- Internal reference: DOV-9223
- CWE: CWE-1050 (Excessive Platform Resource Consumption within a Loop)
- Discovery date: 2026-05-05
Description
Sieve CPU resource usage is tracked in the compiled script, so an attacker that has valid credentials can reset the accounting by repeatedly changing the active script. Compiled script files are also not removed when a script is deleted or renamed.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.15 <2.3.22.2 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L | 3.1 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L | 3.1 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L | 3.1 |
| OX Dovecot CE core >=2.3.15 <2.4.5 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L | 3.1 |
Threats
Impact
The configured Sieve CPU limit can be bypassed, allowing sustained CPU consumption, and the leftover files increase disk consumption. Both can cause degradation of service for mail delivery.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Monitor system for abnormal CPU usage and disk consumption. Update to non-vulnerable version.
CVE-2026-42392: imap-urlauth leaks memory into user-visible error messages
- CVE reference: CVE-2026-42392
- Internal reference: DOV-9230
- CWE: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)
- Discovery date: 2026-05-06
- Researcher credits: djvirus@yeswehack
Description
An attacker that has valid credentials can send an invalid IMAP URLFETCH command, which causes uninitialized memory to be included in the error response returned to the client.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N | 4.3 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N | 4.3 |
Threats
Impact
Process memory contents can be disclosed to the client, which may include sensitive data.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Disable the IMAP URLAUTH functionality. Update to non-vulnerable version.
CVE-2026-73208: auth: db-oauth2: aud claim used as fallback for missing scope claim
- CVE reference: CVE-2026-73208
- Internal reference: DOV-9309
- CWE: CWE-287 (Improper Authentication)
- Discovery date: 2026-05-28
Description
An attacker that holds a token intended for a different purpose can authenticate, because when an OAuth2 token response does not contain a scope claim, the audience claim is used in its place and checked against the configured required scopes. These are different concepts, and the audience claim does not describe what a token is allowed to do.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.13 <2.3.22.2 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N | 7.4 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N | 7.4 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N | 7.4 |
| OX Dovecot CE core >=2.3.13 <2.4.5 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N | 7.4 |
Threats
Impact
A token that grants no relevant permissions can be accepted because its intended recipient value happens to match a configured scope name, granting access that should have been denied. It also hides an identity provider misconfiguration where scopes are not being issued at all.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Ensure the identity provider issues a scope claim for all tokens used with Dovecot, and that configured scope names do not match audience values. Update to non-vulnerable version.
CVE-2026-73209: imap-login crash: Self-recursion on zero-output decompress chunks
- CVE reference: CVE-2026-73209
- Internal reference: DOV-9401
- CWE: CWE-674 (Uncontrolled Recursion)
- Discovery date: 2026-06-10
Description
An attacker that has valid credentials can send crafted compressed data that causes the affected process to exhaust its stack and crash.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | 6.5 |
Threats
Impact
The affected process is terminated, which can cause degradation or denial of service for IMAP.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Update to non-vulnerable version.
CVE-2026-42391: imap: Pre-login memory/CPU growth with ID command
- CVE reference: CVE-2026-42391
- Internal reference: DOV-9529
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-07-04
Description
An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.0 <2.3.22.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
| OX Dovecot CE core >=2.3.0 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
Threats
Impact
The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Limit the number of connections handled by a single imap-login process. This has a performance impact though. Update to non-vulnerable version.
CVE-2026-52687: IMAP: COMPRESS ZSTD can cause excessive memory usage
- CVE reference: CVE-2026-52687
- Internal reference: DOV-9530
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-07-04
Description
An attacker that has valid credentials can select a compression algorithm for the IMAP connection whose decompression state requires a large amount of memory, and open several such connections.
Product status
Affected versions
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core >=2.3.11 <2.3.22.2 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot Pro core >=3.0.0 <3.0.7 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot Pro core >=3.1.0 <3.1.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | 6.5 |
| OX Dovecot CE core >=2.3.11 <2.4.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | 6.5 |
Threats
Impact
The memory limit of the process is reached with only a few connections, terminating the process and all connections it handles, which can cause degradation or denial of service for IMAP.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-08-26)
For products
- OX Dovecot Pro core 3.0.7
- OX Dovecot Pro core 2.3.22.2
- OX Dovecot Pro core 3.1.6
- OX Dovecot CE core 2.4.5
Disable IMAP compression. Alternatively limit the number of connections handled by a single imap-login process, though this has a performance impact. Update to non-vulnerable version.