Quick answers
- Is CVE-2026-109731 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-109731 being exploited in the wild.
- How severe is CVE-2026-109731?
- Informational severity, published 13 October 2026.
- Which products and versions are affected?
- Mozilla Firefox before 158; Mozilla Firefox ESR before 153.5; Mozilla Thunderbird before 158; Mozilla Thunderbird ESR before 153.5.
- Is there a fix for CVE-2026-109731?
- Yes: fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird ESR 153.5. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-109731 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-109731?
- Check whether you run Mozilla Firefox, Mozilla Firefox ESR, Mozilla Thunderbird or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird ESR 153.5
Technical details
An incorrect boundary condition vulnerability exists in the Graphics: Canvas2D component of Firefox and Thunderbird. The vulnerability allows an attacker to trigger out-of-bounds memory access through malicious web content, potentially leading to information disclosure or code execution. This is a client-side vulnerability requiring user interaction (visiting a malicious website).
Affected products
- Mozilla Firefox before 158
- Mozilla Firefox ESR before 153.5
- Mozilla Thunderbird before 158
- Mozilla Thunderbird ESR before 153.5
Timeline
- 2026-10-13: disclosed