Vulnerability 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.
CVSS Score
7.5
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Thunderbird | < 140.15.0 |
Related Weaknesses (CWE)
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2063964Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2026-86/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-87/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-88/Vendor Advisory
FAQ
What is CVE-2026-84640?
CVE-2026-84640 is a vulnerability with a CVSS score of 7.5 (HIGH). 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.
How severe is CVE-2026-84640?
CVE-2026-84640 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-84640?
Check the references section above for vendor advisories and patch information. Affected products include: Mozilla Thunderbird.