Is CVE-2026-27855 in the CISA KEV catalog?

No. CVE-2026-27855 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-27855?

CVE-2026-27855 has a CVSS v3 base score of 6.8 (MEDIUM).

What is the EPSS score for CVE-2026-27855?

CVE-2026-27855 has an EPSS score of 0.34% (26th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-27855?

Upgrade dovecot on debian 11 to 1:2.3.13+dfsg1-2+deb11u3 or later. Fixes are available for 3 affected products.

CVE & CISA-KEV Catalog

CVE-2026-27855

MEDIUM

6.8

CVSS v3

NVD

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.

CWE-294

How to fix

Remediation Available

dovecotDebian

Fixed in:1:2.3.13+dfsg1-2+deb11u3CVE-2026-27855

Fixed in:1:2.3.19.1+dfsg1-2.1+deb12u2CVE-2026-27855

Fixed in:1:2.4.1+dfsg1-6+deb13u4CVE-2026-27855

Fixed in:1:2.4.3+dfsg1-1CVE-2026-27855

dovecotUbuntu

Fixed in:1:2.3.16+dfsg1-3ubuntu2.7USN-8136-1

Fixed in:1:2.3.21+dfsg1-2ubuntu6.3USN-8136-1

Fixed in:1:2.4.1+dfsg1-5ubuntu4.1USN-8136-1

dovecot-coreUbuntu

Fixed in:1:2.3.16+dfsg1-3ubuntu2.7USN-8136-1

Fixed in:1:2.3.21+dfsg1-2ubuntu6.3USN-8136-1

Fixed in:1:2.4.1+dfsg1-5ubuntu4.1USN-8136-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Exploit Intelligence

0.34%probability of exploitation in 30 days

26thpercentile

Low risk: more likely to be exploited than 26% of all known CVEs.

References

Vendor Advisory1

documentation.open-xchange.com

Embed a live status badge for CVE-2026-27855

Markdown

[![CVE-2026-27855](https://tridentstack.com/cve/badge/CVE-2026-27855.svg)](https://tridentstack.com/cve/CVE-2026-27855)

HTML

<a href="https://tridentstack.com/cve/CVE-2026-27855"><img src="https://tridentstack.com/cve/badge/CVE-2026-27855.svg" alt="CVE-2026-27855"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

Start free

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-29.