OXDC-ADV-2026-0001
Metadata
- Document type: OX Dovecot Security Advisory
- Publisher: Open-Xchange GmbH
- Classification: TLP:GREEN
- Publication Date: 2026-03-27
- Current version: 2
- Version status: Final
- Aggregate severity: High
References
Vulnerabilities
CVE-2025-30189: v2.4 regression: auth cache broken with several passdb / userdb
- CVE reference: CVE-2025-30189
- Internal reference: DOV-7830
- CWE: CWE-1250 (Improper Preservation of Consistency Between Independent Representations of Shared State)
- Discovery date: 2025-07-24
- Researcher credits: Erik <erik@broadlux.com>
Description
When cache is enabled, some passdb/userdb drivers incorrectly cache all users with same cache key, causing wrong cached information to be used for these users.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 3.1.0 | 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 2.4.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N | 7.4 |
Threats
Impact
After cached login, all subsequent logins are for same user.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 2.4.1
Install fixed version or disable caching either globally or for the impacted passdb/userdb drivers.
CVE-2025-59028: Invalid base64 authentication can cause DoS for other logins
- CVE reference: CVE-2025-59028
- Internal reference: DOV-8349
- CWE: CWE-20 (Improper Input Validation)
- Discovery date: 2025-11-04
Description
When sending invalid base64 SASL data, login process is disconnected from the auth server, causing all active authentication sessions to fail.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 3.1.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | 5.3 |
| OX Dovecot Pro core 2.4.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | 5.3 |
Threats
Impact
Invalid BASE64 data can be used to DoS a vulnerable server to break concurrent logins.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 3.1.2
- OX Dovecot Pro core 2.4.3
Install fixed version or disable concurrency in login processes (heavy perfomance penalty on large deployments).
CVE-2025-59032: v2.4/v3.1 regression: Pigeonhole: ManageSieve panic occurs with sieve-connect as a client
- CVE reference: CVE-2025-59032
- Internal reference: DOV-8508
- CWE: CWE-20 (Improper Input Validation)
- Discovery date: 2025-11-29
Description
ManageSieve AUTHENTICATE command crashes when using literal as SASL initial response.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 3.1.0 | 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 2.4.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
Threats
Impact
This can be used to crash ManageSieve service repeatedly, making it unavailable for other users.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 2.4.3
- OX Dovecot Pro core 3.1.3
Control access to ManageSieve port, or disable the service if it's not needed. Alternatively upgrade to a fixed version.
CVE-2025-59031: decode2text.sh OOXML extraction may follow symlinks and read unintended files during indexing
- CVE reference: CVE-2025-59031
- Internal reference: DOV-8584
- CWE: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)
- Discovery date: 2025-12-29
- Researcher credits: cavid@yeswehack
Description
Dovecot has provided a script to use for attachment to text conversion. This script unsafely handles zip-style attachments.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 2.3.0 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N | 4.3 |
Threats
Impact
Attacker can use specially crafted OOXML documents to cause unintended files on the system to be indexed and subsequently ending up in FTS indexes.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 2.4.3
- OX Dovecot Pro core 3.1.3
- OX Dovecot Pro core 2.3.22.1
Do not use the provided script, instead, use something else like FTS tika.
CVE-2026-0394: auth: Path traversal in passwd-file passdb using %d (domain) escapes base directory and opens /etc/passwdPre-auth path traversal in passwd-file passdb using %d (domain) escapes base directory and opens /etc/passwd
- CVE reference: CVE-2026-0394
- Internal reference: DOV-8591
- CWE: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'))
- Discovery date: 2026-01-07
- Researcher credits: strokep@yeswehack
Description
When dovecot has been configured to use per-domain passwd files, and they are placed one path component above /etc, or slash has been added to allowed characters, path traversal can happen if the domain component is directory partial.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 2.3.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N | 5.3 |
Threats
Impact
This allows inadvertently reading /etc/passwd (or some other path which ends with passwd). If this file contains passwords, it can be used to authenticate wrongly, or if this is userdb, it can unexpectly make system users appear valid users.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 3.1.0
- OX Dovecot Pro core 2.4.0
Upgrade to fixed version, or use different authentication scheme that does not rely on paths. Alternatively you can also ensure that the per-domain passwd files are in some other location, such as /etc/dovecot/auth/%d.
CVE-2026-27860: v2.4/v3.1 regression: auth-ldap is not escaping usernames
- CVE reference: CVE-2026-27860
- Internal reference: DOV-8775
- CWE: CWE-90 (Improper Neutralization of Special Elements used in an LDAP Query ('LDAP Injection'))
- Discovery date: 2026-02-20
- Researcher credits: cookiejack15@yeswehack
Description
If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP authentication.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 3.1.0 | 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 2.4.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | 3.7 |
Threats
Impact
This leads to potentially bypassing restrictions and allows probing of LDAP structure.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 2.4.3
- OX Dovecot Pro core 3.1.4
Do not clear out auth_username_chars, or install fixed version.
CVE-2026-24031: v2.4/v3.1 regression: SQL injection allows bypassing authentication
- CVE reference: CVE-2026-24031
- Internal reference: DOV-8781
- CWE: CWE-89 (Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection'))
- Discovery date: 2026-02-23
- Researcher credits: whisperer@yeswehack
Description
Dovecot SQL based authentication can be bypassed when auth_username_chars is cleared by admin.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 3.1.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L | 7.7 |
| OX Dovecot Pro core 2.4.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L | 7.7 |
Threats
Impact
This vulnerability allows bypassing authentication for any user and user enumeration.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 2.4.3
- OX Dovecot Pro core 3.1.4
Do not clear auth_username_chars. If this is not possible, install latest fixed version.
CVE-2026-27859: v3.0.2+ regression: Message headers MIME parameter parsing can cause excessive CPU usage
- CVE reference: CVE-2026-27859
- Internal reference: DOV-8787
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-02-24
- Researcher credits: djvirus@yeswehack
Description
A mail message containing excessive amount of RFC 2231 MIME parameters causes LMTP to use too much CPU.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 3.0.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | 5.3 |
| OX Dovecot Pro core 3.1.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | 5.3 |
| OX Dovecot Pro core 2.4.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | 5.3 |
Threats
Impact
A suitably formatted mail message causes mail delivery process to consume large amounts of CPU time.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 3.0.5
- OX Dovecot Pro core 2.4.3
- OX Dovecot Pro core 3.1.4
Use MTA capabilities to limit RFC 2231 MIME parameters in mail messages, or upgrade to fixed version where the processing is limited.
CVE-2026-27857: imap-login: Excessive memory usage DoS
- CVE reference: CVE-2026-27857
- Internal reference: DOV-8816
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-02-27
- Researcher credits: whisperer@yeswehack
Description
Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 2.3.0 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L | 4.3 |
Threats
Impact
Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 3.0.5
- OX Dovecot Pro core 2.4.3
- OX Dovecot Pro core 3.1.4
- OX Dovecot Pro core 2.3.22.1
Install fixed version, there is no other remediation.
CVE-2026-27858: managesieve-login out-of-memory DoS
- CVE reference: CVE-2026-27858
- Internal reference: DOV-8818
- CWE: CWE-400 (Uncontrolled Resource Consumption)
- Discovery date: 2026-02-28
- Researcher credits: ilyar@yeswehack
Description
Attacker can send a specifically crafted message before authentication that causes managesieve to allocate large amount of memory.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 2.3.0 | 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 | 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 2.4.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 7.5 |
Threats
Impact
Attacker can force managesieve-login to be unavailable by repeatedly crashing the process.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 3.0.5
- OX Dovecot Pro core 2.4.3
- OX Dovecot Pro core 3.1.4
- OX Dovecot Pro core 2.3.22.1
Protect access to managesieve protocol, or install fixed version.
CVE-2026-27856: doveadm: Credentials verified without timing safety
- CVE reference: CVE-2026-27856
- Internal reference: DOV-8830
- CWE: CWE-287 (Improper Authentication)
- Discovery date: 2026-03-04
- Researcher credits: bksparajuli@yeswehack
Description
Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack. An attacker can use this to determine the configured credentials.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 2.3.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N | 7.4 |
Threats
Impact
Figuring out the credential will lead into full access to the affected component.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 3.0.5
- OX Dovecot Pro core 2.4.3
- OX Dovecot Pro core 3.1.4
- OX Dovecot Pro core 2.3.22.1
Limit access to the doveadm http service port, install fixed version.
CVE-2026-27855: auth: OTP driver vulnerable to replay attack
- CVE reference: CVE-2026-27855
- Internal reference: DOV-8859
- CWE: CWE-294 (Authentication Bypass by Capture-replay)
- Discovery date: 2026-03-09
- Researcher credits: hamizanazman@yeswehack
Description
Dovecot OTP authentication is vulnerable to replay attack under specific conditions. If auth cache is enabled, and username is altered in passdb, then OTP credentials can be cached so that same OTP reply is valid.
Product status
Last affected
| Products | CVSS-Vector | CVSS Base Score |
|---|---|---|
| OX Dovecot Pro core 2.3.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N | 6.8 |
Threats
Impact
An attacker able to observe an OTP exchange is able to log in as the user.
Exploit status
No publicly available exploits are known.
Remediation
Vendor fix (2026-03-27)
For products
- OX Dovecot Pro core 2.4.3
If authentication happens over unsecure connection, switch to SCRAM protocol. Alternatively ensure the communcations are secured, and if possible switch to OAUTH2 or SCRAM.