High severity7.5NVD Advisory· Published Sep 1, 2026· Updated Sep 3, 2026
CVE-2026-84640
CVE-2026-84640
Description
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.
Affected products
3- osv-coords2 versions
< 140.15.0-1.1+ 1 more
- (no CPE)range: < 140.15.0-1.1
- (no CPE)range: < 140.16.0-1.el9_8.alma.1
- Range: Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2
Patches
Vulnerability mechanics
References
4- www.mozilla.org/security/advisories/mfsa2026-86/nvdVendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-87/nvdVendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-88/nvdVendor Advisory
- bugzilla.mozilla.org/show_bug.cginvdPermissions Required
News mentions
1- Mozilla Thunderbird: 16 Vulnerabilities Including Critical Sandbox Escapes Disclosed TogetherVypr Intelligence · Sep 1, 2026