CVE-2026-109740 The advisory has been revoked - it doesn't affect any version of package firefox-esr (opens in a new tab)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-DEBIANUNSTABLE-FIREFOXESR-20887177
- published14 Oct 2026
- disclosed13 Oct 2026
Introduced: 13 Oct 2026
NewCVE-2026-109740 (opens in a new tab)Amendment
The Debian security team deemed this advisory irrelevant for Debian:unstable.
NVD Description
Note: Versions mentioned in the description apply only to the upstream firefox-esr package and not the firefox-esr package as distributed by Debian.
Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
References
- https://security-tracker.debian.org/tracker/CVE-2026-109740
- https://bugzilla.mozilla.org/show_bug.cgi?id=2057113
- https://www.mozilla.org/security/advisories/mfsa2026-106/
- https://www.mozilla.org/security/advisories/mfsa2026-108/
- https://www.mozilla.org/security/advisories/mfsa2026-109/
- https://www.mozilla.org/security/advisories/mfsa2026-110/