CVE-2026-74989 PUBLISHED

Internally found bugs present in Thunderbird 153. 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 154 and Thunderbird 154.

• Christian Holler, Ryan Hunt, Tom Ritter and the Mozilla Fuzzing Team

• Low Severity internally found bugs fixed in Thunderbird 154
• Moderate Severity internally found bugs fixed in Thunderbird 154
• https://www.mozilla.org/security/advisories/mfsa2026-74/
• https://www.mozilla.org/security/advisories/mfsa2026-78/