PatchTheCVECVE-2026-27855: Dovecot OTP authentication is vulnerable to replay attack under specific conditions
CVE-2026-27855 is a medium-severity flaw (CVSS 6.8) affecting dovecot, dovecot. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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. An attacker able to observe an OTP exchange is able to log in as the user. If authentication happens over unsecure connection, switch to SCRAM protocol. Alternatively ensure the communcations are secured, and if possible switch to OAUTH
Why this priority
- No elevated risk signals yet
A fixed release or distro patch exists.
Risk facts
| CVSS score | 6.8 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | High |
| Privileges needed | None |
| User interaction | Required |
| EPSS exploit chance | 0.3% (top 76%) |
| CISA exploited list | No |
| Weakness | CWE-294 |
| Published | 2026-03-27 |
| Last modified | 2026-10-26 |
Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-27855?
dovecot: upgrade to 2.4.3; dovecot: upgrade to newer than 2.3.0. Exact commands for each OS are on this page.
Is CVE-2026-27855 being exploited?
CVE-2026-27855 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-27855 affect?
CVE-2026-27855 affects dovecot, dovecot. Severity is medium (CVSS 6.8). 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. An attacker able to observ
How urgent is CVE-2026-27855?
Priority 30/100. No elevated risk signals yet.
Software pages
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