CVE-2026-4371

HIGH 7.4

Out of bounds read in IMAP parsing

CVSS Score

7.4

EPSS Score

0.0%

EPSS Percentile

0th

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.

Vendor	mozilla
Product	thunderbird
Ecosystems	Browser JavaScript
Industries	Technology
Published	Mar 24, 2026
Last Updated	Apr 13, 2026

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Affected Versions

Mozilla / Thunderbird

All versions affected

References

NVD ↗ CVE.org ↗ EPSS Data ↗

bugzilla.mozilla.org: https://bugzilla.mozilla.org/show_bug.cgi?id=2023493 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-23/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-24/

Credits

Rintaro Kobayashi