Executive brief
Firefox is a widely-used web browser that millions of people rely on for internet access. This vulnerability could allow an attacker to execute arbitrary code on a user's computer by exploiting a memory safety flaw in the text rendering component. Successful exploitation could lead to complete compromise of the affected system.
Technical details
This is a use-after-free vulnerability in the Graphics: Text component of Firefox. The defect allows an attacker to reference memory that has been deallocated, potentially enabling code execution. The vulnerability can be triggered through web content, requiring only that a user visit a malicious website. The issue has been patched in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
Affected products
- Mozilla Firefox before 154
- Mozilla Firefox ESR 115.x before 115.39, 140.x before 140.14, 153.x before 153.1
- Mozilla Thunderbird before 154, 140.x before 140.14, 153.x before 153.1
Timeline
- 2026-08-18: disclosed
- 2026-08-18: patched: Fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, Thunderbird 153.1