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DovecotApplication

CVE-2026-27851

CRITICAL · 9.1 CVSS v3.1 Published 2026-05-12
Fix available
A fix is available. Upgrade to 2.4.4 / 3.1.5 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A vulnerability in template rendering allows the 'safe' filter (which marks content as exempt from escaping) to incorrectly propagate its 'safe' status to all subsequent pipelines on the same string. When combined with variable expansion, this causes unsanitized user input to be unescaped, enabling SQL or LDAP injection when the affected output is used in authentication contexts.

MitigationAvoid using the safe filter in templates until a patched version is available. Audit existing templates for safe filter usage with variable expansion, particularly in authentication-related code paths.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
DovecotApplication
Affected:< 2.4.4
DovecotApplication
Affected:< 3.1.5

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Dovecot version
    Run 'dovecot --version' or check package manager (rpm -q dovecot, dpkg -l dovecot)
    Affected if Version is below 2.4.4 for Dovecot or below 3.1.5 for Open Xchange Dovecot
  2. Locate template configuration files
    Search for template files in /etc/dovecot, /usr/share/dovecot, or custom template directories; look for .tpl, .template, or Sieve script files
    Affected if Templates exist and are used for user-facing content or authentication
  3. Identify safe filter usage in templates
    Grep for '|safe' or 'safe_filter' within template files found in the system
    Affected if Templates contain the 'safe' filter applied to variables
  4. Check for variable expansion in authentication contexts
    Review template content for variables ({{var}} or similar) used in authentication flows, password templates, or login screens; grep for 'safe' near auth-related keywords
    Affected if The safe filter is applied to variables that could contain user input in authentication-related templates
  5. Audit SQL/LDAP query construction
    Search configuration for SQL or LDAP query patterns in authentication modules; check if templates feed into query parameters without parameterization
    Affected if User-controllable data from templates flows into SQL or LDAP queries without proper sanitization

You are affected if running a vulnerable Dovecot version AND templates with the 'safe' filter are used in authentication or query contexts where user input flows through.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.4.4 / 3.1.5 or later
Fixed in 2.4.43.1.5
Interim mitigation

Avoid using the safe filter in templates until a patched version is available. Audit existing templates for safe filter usage with variable expansion, particularly in authentication-related code paths.

Recommended fix High confidence

Dovecot 2.4.4 (for 2.x branch) or Dovecot 3.1.5 (for 3.x branch) or later

  1. Check the current installed Dovecot version using: dovecot --version
  2. Identify which major version branch is in use (2.x or 3.x)
  3. For Debian/Ubuntu: Update package lists and upgrade: apt update && apt install --only-upgrade dovecot-core
  4. For RHEL/CentOS: yum update dovecot or dnf update dovecot
  5. For RHEL 8/9: Verify available fixed version in repositories: dnf info dovecot
  6. After upgrade, verify the new version is installed: dovecot --version
  7. Restart Dovecot service: systemctl restart dovecot (or service dovecot restart)
  8. If using safe filter with variable expansion in configuration, review and test authentication workflows after upgrade
Caveat Review Dovecot upgrade notes for your distribution; minor version upgrades typically preserve configuration but test mail flow after upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Dovecot Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,880
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,808.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-27851 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data