dbcve.org
Debian LinuxOperating system · Debian

CVE-2020-12137

MEDIUM · 6.1 CVSS v3.1 Published 2020-04-24
Fix available
A fix is available. Upgrade to 2.1.30 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

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.x before 2.1.30 uses the .obj extension for scrubbed application/octet-stream MIME parts. This behavior may contribute to XSS attacks against list-archive visitors, because an HTTP reply from an archive web server may lack a MIME type, and a web browser may perform MIME sniffing, conclude that the MIME type should have been text/html, and execute JavaScript code.

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 · high confidence

GNU Mailman 2.x before 2.1.30 uses the .obj extension for scrubbed application/octet-stream MIME parts in list archives. When web servers serve these files without proper Content-Type headers, browsers may perform MIME sniffing and incorrectly interpret them as text/html, enabling stored XSS attacks against visitors viewing archived mailing list content.

MitigationUpgrade Mailman 2.x to version 2.1.30 or later, and configure the archive web server to send explicit Content-Type headers (e.g., Content-Type: application/octet-stream) for scrubbed MIME parts to prevent MIME sniffing attacks.

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
Debian LinuxOperating system
Affected:= 9.0= 10.0= 8.0
FedoraOperating system
Affected:= 31= 32
Ubuntu LinuxOperating system
Affected:= 16.04= 18.04
MailmanApplication
Affected:>= 2.0, < 2.1.30
Backports SleApplication
Affected:= 15.0
LeapOperating system
Affected:= 15.2

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
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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. Check Mailman version
    Run 'mailman --version' or check the version file typically at /var/lib/mailman/Mailman/Version.py or through your package manager
    Affected if Version is 2.x and less than 2.1.30
  2. Verify archives are enabled
    Check the Mailman list configuration for the 'archive' attribute, typically in /var/lib/mailman/lists/<listname>/config.db or via 'mailman lists' and 'mailman info <listname>'
    Affected if Archives are enabled and storing archived mailing list content accessible via web
  3. Inspect archived MIME parts for .obj extension
    Browse the archive directory (typically /var/lib/mailman/archives/public/<listname>/ or /var/lib/mailman/archives/private/<listname>/) and look for files with .obj extension that were scrubbed from application/octet-stream attachments
    Affected if Archive directories contain .obj files served without Content-Type headers
  4. Check web server configuration for archive MIME types
    Inspect the web server (Apache, nginx, etc.) configuration that serves the Mailman archives and verify if it sends explicit Content-Type headers for .obj files or has proper MIME type mappings for application/octet-stream
    Affected if Web server serves .obj files without explicit Content-Type: application/octet-stream header, allowing browsers to MIME sniff and interpret as text/html

You are affected if running Mailman 2.x before 2.1.30 with archives enabled, where .obj files from scrubbed MIME parts are served by a web server without explicit Content-Type headers, allowing browsers to potentially execute XSS via MIME sniffing.

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.

From vendor data
Upgrade available Upgrade to 2.1.30 or later
Fixed in 2.1.30
Interim mitigation

Upgrade Mailman 2.x to version 2.1.30 or later, and configure the archive web server to send explicit Content-Type headers (e.g., Content-Type: application/octet-stream) for scrubbed MIME parts to prevent MIME sniffing attacks.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

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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-2020-12137 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