CVE-2021-29949: Mozilla Thunderbird

High severity, CVSS 7.8. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Mozilla Thunderbird: before 78.9.1 (fixed in 78.9.1)

Published 2021-06-24. Last modified 2026-06-17.