What’s Vulnerable › Vulnerabilities

CVE-2021-43529

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-02-16 · updated 2026-06-17
• Weakness: CWE-787

Description

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

How to fix

Upgrade to a fixed version: Mozilla Thunderbird 91.3.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=CVE-2021-43529
• https://bugzilla.mozilla.org/show_bug.cgi?id=CVE-2021-43529

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