CVE-2026-103500

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.

CVSS 3.1

6.1CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H

EPSS

0.3% chance of exploitation in the next 30 days; higher than 19% of CVEs (scores of 2026-10-25)

CWEs

CWE-787, CWE-122

Published

2026-09-30

Modified

2026-10-16

Record from

the NVD, synced 2026-10-19

Affected

• mozilla:thunderbird

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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