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Fencer Vulns
medium 6.1

CVE-2020-12137 json

GNU Mailman 2.x before 2.1.30 uses the .obj extension for scrubbed application/octet-stream MIME parts.

published 2020-04-24 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-4452

cvss
6.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.3%
EPSS 2.3% chance of exploitation in 30 days, percentile 83%
public exploits
0
none known

Summary

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.

Patch / fix

  • gnu mailman 2.1.30
  • mailman Ubuntu 16.04 LTS 1:2.1.20-1ubuntu0.4
  • mailman Ubuntu 18.04 LTS 1:2.1.26-1ubuntu0.1
  • mailman Ubuntu 20.04 LTS 1:2.1.29-1ubuntu3.1

ubuntu advisories UBUNTU-CVE-2020-12137

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • mailman RHEL 8 3:2.1.29-10.module+el8.3.0+6860+8e47d84b

red hat advisories RHSA-2020:4667

  • mailman SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +14 more 2.1.17-3.20.1
  • mailman SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 2.1.15-9.6.20.1

suse advisories SUSE-SU-2020:1301-1SUSE-SU-2020:14356-1

  • mailman Package Hub 15 SP2 2.1.34-bp152.7.3.1
  • mailman openSUSE Leap 15.2 2.1.34-lp152.7.3.1

opensuse advisories openSUSE-SU-2020:1752-1openSUSE-SU-2020:1707-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-12137 updated cvss 6.1

mailman: XSS via file attachments in list archives

  • Red Hat Enterprise Linux 5 mailman Red Hat Enterprise Linux 6 mailman
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 mailman
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux AppStream (v. 8) mailman 2.1.29-10.module+el8.3.0+6860+8e47d84b
    fixed: vendor fix RHSA-2020:4667

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.29% chance of exploitation in the next 30 days, higher than 83% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.