Description
A maliciously constructed mail header could lead to multiple fields being parsed as one, or potential memory safety violations. This vulnerability was fixed in Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.
Affected products
mozilla: thunderbird
References4
- www.mozilla.org/security/advisories/mfsa2026-94/ Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-95/ Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-96/ Vendor Advisory
- bugzilla.mozilla.org/show_bug.cgi?id=2060601 Permissions Required
Metrics
- CVSS 3.1
-
9.8
CRITICAL
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 1% percentile: 46 · as of 7 November 2026
- CWE
- CWE-444
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.