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Fencer Vulns
high 7.8

CVE-2021-29949 json

When loading the shared library that provides the OTR protocol implementation, Thunderbird will initially attempt to open it using a filena…

published 2021-06-24 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-16408

cvss
7.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits
0
none known

Summary

When loading the shared library that provides the OTR protocol implementation, Thunderbird will initially attempt to open it using a filename that isn't distributed by Thunderbird. If a computer has already been infected with a malicious library of the alternative filename, and the malicious library has been copied to a directory that is contained in the search path for executable libraries, then Thunderbird will load the incorrect library. This vulnerability affects Thunderbird < 78.9.1.

Patch / fix

  • Mozilla Thunderbird 78.9.1
  • thunderbird Debian 14, Debian 13, Debian 12 1:78.10.0-1

debian advisories DEBIAN-CVE-2021-29949

  • thunderbird Ubuntu 18.04 LTS 1:78.11.0+build1-0ubuntu0.18.04.2
  • thunderbird Ubuntu 20.04 LTS 1:78.11.0+build1-0ubuntu0.20.04.2

ubuntu advisories UBUNTU-CVE-2021-29949

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

  • thunderbird RHEL 8 78.9.1-1.el8_3
  • thunderbird RHEL 7 78.9.1-1.el7_9
  • thunderbird RHEL 8.2 EUS 78.9.1-1.el8_2
  • thunderbird RHEL 8.1 EUS 78.9.1-1.el8_1

red hat advisories RHSA-2021:1201RHSA-2021:1193RHSA-2021:1192RHSA-2021:1190

  • thunderbird Arch Linux 78.9.1-1

arch linux advisories AVG-1790

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-2021-29949 updated cvss 7.8

Mozilla: Thunderbird might execute an alternative OTR library

  • Red Hat Enterprise Linux 6 thunderbird
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) thunderbird 78.9.1-1.el8_3
    fixed: vendor fix RHSA-2021:1193
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird 78.9.1-1.el8_1
    fixed: vendor fix RHSA-2021:1190
  • Red Hat Enterprise Linux AppStream EUS (v. 8.2) thunderbird 78.9.1-1.el8_2
    fixed: vendor fix RHSA-2021:1201
  • Red Hat Enterprise Linux Client (v. 7) thunderbird 78.9.1-1.el7_9 Red Hat Enterprise Linux Server Optional (v. 7) thunderbird 78.9.1-1.el7_9 Red Hat Enterprise Linux Workstation (v. 7) thunderbird 78.9.1-1.el7_9
    fixed: vendor fix RHSA-2021:1192

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

0.32% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD 2.0 4.4 AV:L/AC:M/Au:N/C:P/I:P/A:P

Affected products

  • Mozilla Thunderbird

Classification

Weakness
  • CWE-427 Uncontrolled Search Path Element

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.