CVE-2026-27851: When safe filter is used with variable expansion, all following pipelines on the same string are incorrectly i

Q: How do I fix CVE-2026-27851?

dovecot: upgrade to 2.4.4; dovecot: upgrade to 3.1.5. Exact commands for each OS are on this page.

Q: Is CVE-2026-27851 being exploited?

CVE-2026-27851 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-27851 affect?

CVE-2026-27851 affects dovecot, dovecot. Severity is high (CVSS 7.4). When safe filter is used with variable expansion, all following pipelines on the same string are incorrectly interpreted as safe too, enabling unsafe data to be unescaped. This can enable SQL / LDAP injection attacks when used in authentica

Q: How urgent is CVE-2026-27851?

Priority 40/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.4REMOTEUPGRADEUPGRADE

CVE-2026-27851 is a high-severity flaw (CVSS 7.4) affecting dovecot, dovecot. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

When safe filter is used with variable expansion, all following pipelines on the same string are incorrectly interpreted as safe too, enabling unsafe data to be unescaped. This can enable SQL / LDAP injection attacks when used in authentication. Avoid using safe filter until on fixed version. No publicly available exploits are known.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.4 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 65%)
CISA exploited list	No
Weakness	CWE-235, CWE-89
Published	2026-05-12
Last modified	2026-10-26

Publisher (CNA): Open-Xchange · Vendor: dovecot · open-xchange

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-12 14:16 UTCPublished CVE record published
2026-10-26 18:10 UTCUpdated Record last modified

dovecot dovecot UPGRADE

Affected: < 2.4.4

Fixed in: 2.4.4

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy dovecot || rpm -q dovecot || dovecot --version

2. UPGRADE to 2.4.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade dovecot

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade dovecot

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

open-xchange dovecot UPGRADE

Affected: < 3.1.5

Fixed in: 3.1.5

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy dovecot || rpm -q dovecot || dovecot --version

2. UPGRADE to 3.1.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade dovecot

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade dovecot

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
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-2026-27851?

dovecot: upgrade to 2.4.4; dovecot: upgrade to 3.1.5. Exact commands for each OS are on this page.

Is CVE-2026-27851 being exploited?

CVE-2026-27851 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-2026-27851 affect?

CVE-2026-27851 affects dovecot, dovecot. Severity is high (CVSS 7.4). When safe filter is used with variable expansion, all following pipelines on the same string are incorrectly interpreted as safe too, enabling unsafe data to be unescaped. This can enable SQL / LDAP injection attacks when used in authentica

How urgent is CVE-2026-27851?

Priority 40/100. High severity; Remotely exploitable, no login, no user action

Software pages

Dovecot vulnerabilities

Related CVEs

CVE-2026-27855 MEDIUM 6.8 UPGRADE UPGRADE Dovecot OTP authentication is vulnerable to replay attack under specific conditions
CVE-2026-27857 MEDIUM 4.3 UPGRADE UPGRADE Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage
CVE-2026-27858 HIGH 7.5 UPGRADE UPGRADE Attacker can send a specifically crafted message before authentication that causes managesieve to allocate lar
CVE-2026-24031 HIGH 7.7 UPGRADE UPGRADE Dovecot SQL based authentication can be bypassed when auth_username_chars is cleared by admin
CVE-2026-27856 HIGH 7.4 UPGRADE UPGRADE Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack

References

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