CVE-2026-84640

UNKNOWN 0.0

One byte overflow read in mail parser

CVSS Score

0.0

EPSS Score

0.0%

EPSS Percentile

0th

A maliciously constructed mail header could lead to a one byte read past the end of a buffer. This vulnerability was fixed in Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

Vendor	mozilla
Product	thunderbird
Ecosystems	Browser JavaScript
Industries	Technology
Published	Sep 1, 2026
Last Updated	Sep 1, 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=2063964 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-86/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-87/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-88/

Credits

Ramesh Adhikari, Dr. Faruk Kazi (CoE-CNDS Lab, VJTI, Mumbai, India)