CVE-2021-43529: Mozilla Thunderbird

Critical severity, CVSS 9.8. EPSS: 0.5% chance of exploitation in the next 30 days.

Thunderbird versions prior to 91.3.0 are vulnerable to the heap overflow described in CVE-2021-43527 when processing S/MIME messages. Thunderbird versions 91.3.0 and later will not call the vulnerable code when processing S/MIME messages that contain certificates with DER-encoded DSA or RSA-PSS signatures.

Affected products

• Mozilla Thunderbird: before 91.3.0 (fixed in 91.3.0)

Published 2023-02-16. Last modified 2026-06-17.