CVE-2026-103500

Heap buffer overflow opening large email

State: Published
Severity: 6.3 Medium
Published: Sep 30, 2026
Updated: Oct 21, 2026
Reserved: Sep 30, 2026

Description

An attacker could cause a heap buffer overflow by getting a user to open an email that is greater than or equal to 2GB in size. This vulnerability was fixed in Thunderbird 157, Thunderbird 140.17, and Thunderbird 153.4.

Scores

CVSS	Score	Vector	Source
3.1	6.3 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L	CISA-ADP

Weaknesses

CWE-122 Heap-based Buffer Overflow

Affected Products

Product	Versions
ThunderbirdMozilla	140.17 through 140.Not affected 153.4 through 153.Not affected 157 and laterNot affected

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2070267
https://www.mozilla.org/security/advisories/mfsa2026-101/
https://www.mozilla.org/security/advisories/mfsa2026-102/
https://www.mozilla.org/security/advisories/mfsa2026-103/

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