dbcve.org
MailmanApplication · Gnu

CVE-2025-43920

HIGH · 8.1 CVSS v3.1 Published 2025-04-20
Fix available
A fix is available. Upgrade to after 2.1.39 or later.
See remediation →
90/100
Remediation priority · Urgent
Public exploit 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
GNU Mailman 2.1.39, as bundled in cPanel (and WHM), in certain external archiver configurations, allows unauthenticated attackers to execute arbitrary OS commands via shell metacharacters in an email Subject line. NOTE: multiple third parties report that they are unable to reproduce this, regardless of whether cPanel or WHM is used.

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
How this class of weakness works · CWE-78

User input reaches a shell or system command without being fully separated from the command itself, so an attacker can append their own instructions. Because these run with the application's privileges, it often means full control of the host. The lasting fix is to avoid the shell entirely — call APIs directly and pass arguments as data, never as concatenated strings.

General guidance for the os command injection class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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
MailmanApplication
Affected:>= 2.1.1, <= 2.1.39

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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 a release after 2.1.39
Recommended fix Moderate confidence

Mailman 2.1.40 or later (latest stable 2.1.x release)

  1. 1. Backup your current Mailman installation and configuration before proceeding.
  2. 2. Obtain the latest Mailman 2.1.x release (version 2.1.40 or later) from the official GNU Mailman repository at https://www.gnu.org/software/mailman/ or from your distribution's package manager.
  3. 3. If using a package manager (e.g., apt, yum, dnf), update the package: 'sudo apt-get update && sudo apt-get install mailman' or 'sudo yum update mailman' or 'sudo dnf update mailman'.
  4. 4. If upgrading from source, download the latest tarball, extract it, run './configure', 'make', and 'make install' as documented in the INSTALL file.
  5. 5. After upgrade, verify the Mailman version matches the expected fixed version using 'mailman --version' or checking the admin interface.
  6. 6. Review and test external archiver configurations to ensure they are properly secured and not exposing the vulnerability.
  7. 7. Restart the Mailman service if required by your installation method.
  8. 8. Monitor logs for any suspicious activity and test that legitimate mailing list functions work correctly.
Caveat Review release notes for any configuration changes; minor version upgrades in the 2.1.x series are typically backward compatible but archive format changes may require migration steps

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

We can identify the exact fixed release, upgrade, and verify it in staging — typical engagement from $3,200. Get the upgrade done

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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-2025-43920 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