CVE-2026-14899

UNKNOWN 0.0

Off-by-one out of bounds read in MIME header parser for forwarding

CVSS Score

0.0

EPSS Score

0.0%

EPSS Percentile

0th

The code to parse MIME headers for display when forwarding a message (if the setting to view all headers was enabled) had an off-by-one error, allowing a single byte to be read from the memory after the buffer for the headers, and potentially crashing Thunderbird. This vulnerability was fixed in Thunderbird 153 and Thunderbird 140.13.

Vendor	mozilla
Product	thunderbird
Ecosystems	Browser JavaScript
Industries	Technology
Published	Jul 22, 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=2046137 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-71/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-72/

Credits

Claude, Kai Engert