CVE-2026-4371

Description

A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive data. This vulnerability was fixed in Thunderbird 149 and Thunderbird 140.9.

PUBLISHED Reserved 2026-03-18 | Published 2026-03-24 | Updated 2026-04-13 | Assigner mozilla

Product status

Credits

Rintaro Kobayashi

References

bugzilla.mozilla.org/show_bug.cgi?id=2023493

www.mozilla.org/security/advisories/mfsa2026-23/

www.mozilla.org/security/advisories/mfsa2026-24/

cve.org (CVE-2026-4371)

nvd.nist.gov (CVE-2026-4371)

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