CVE-2026-84142

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.

Score

CVSS 3.1 9.8 Critical

Status

Modified - security@mozilla.org

Published

2026-09-01

Last modified

2026-09-03

Weaknesses

CWE-119, CWE-200

Affected products

• Firefox (Mozilla)
• Thunderbird (Mozilla)

References

• https://bugzilla.mozilla.org/buglist.cgi?bug_id=2029421%2C2040889%2C2045313%2C2045435%2C2053578%2C2058621%2C2058626
• https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048796%2C2053150%2C2057356
• https://www.mozilla.org/security/advisories/mfsa2026-82/
• https://www.mozilla.org/security/advisories/mfsa2026-86/