6.8

CVE-2026-27855: dovecot Authentication Bypass by Capture-replay

CVSS: 6.8v3.1MediumAnalyzed
AliasesALPINE-CVE-2026-27855UBUNTU-CVE-2026-27855DEBIAN-CVE-2026-27855
Published 27-03-2026Last modified 27-03-2026
Open JSON

Vulnerability summary

CVE-2026-27855 is a medium (CVSS 6.8) Authentication Bypass by Capture-replay vulnerability in dovecot. EPSS estimates a 0.39% chance of exploitation in the next 30 days, higher than 31.1% of scored vulnerabilities.

Overall risk
27/100
0100
Medium · default modelHow is this calculated?
CVSS score
6.8/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.39%
0%100%
Low · +0.07 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 4 · Related 5
OPENSUSE-SU-2026:10442-1OPENSUSE-SU-2026:20554-1SUSE-SU-2026:21208-1SUSE-SU-2026:4139-1USN-8136-1

Timeline

  1. 27-03-2026
    PublishedVulnerability first disclosed.
  2. 27-03-2026
    Last modifiedVulnerability information updated.

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. 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 OAUTH2 or SCRAM. No publicly available exploits are known.

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.39%

Chance of exploitation in the next 30 days

Percentile

31%

Versus all other CVEs

30-day change

+0.07 pp

From 0.31% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.39%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Alpine1 product
  • dovecot< 2.4.3-r0
Debian1 product
  • dovecot< 1:2.3.19.1+dfsg1-2.1+deb12u2 | < 1:2.4.1+dfsg1-6+deb13u4 | < 1:2.4.3+dfsg1-1
Dovecot1 product
Open-xchange1 product
Open-xchange gmbh1 product
Ubuntu1 product
  • dovecotAll versions (No fix recorded) | < 1:2.3.16+dfsg1-3ubuntu2.7 | < 1:2.3.21+dfsg1-2ubuntu6.3 | < 1:2.4.1+dfsg1-5ubuntu4.1

6 vendors · 6 products

References

6 links