CVE-2026-84142

critical

Description

Internally found bugs present in Thunderbird 154. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155 and Thunderbird 155.

References

https://www.mozilla.org/security/advisories/mfsa2026-86/

https://www.mozilla.org/security/advisories/mfsa2026-82/

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048796%2C2053150%2C2057356

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2029421%2C2040889%2C2045313%2C2045435%2C2053578%2C2058621%2C2058626

Details

Source: Mitre, NVD

Published: 2026-09-01

Updated: 2026-09-01

Risk Information

CVSS v2

Base Score: 7.5

Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P

Severity: High

CVSS v3

Base Score: 9.8

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

Severity: Critical