CVE-2026-100787
CriticalCVSS 9.6Exploitation Probability (EPSS)
Low risk4th percentile - higher than 4% of all known CVEs
Summary
Vulnerability allows sandbox escape in the XUL component. It was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.
Risk Assessment
Sandbox escape in XUL could allow an attacker to execute code outside browser restrictions, potentially leading to system takeover.
Recommendation
Urgently update Firefox or Thunderbird to the patched versions.
Other vulnerabilities in Firefox
See all- CVE-2026-100829Critical
Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.
- CVE-2026-100828Critical
Mitigation bypass in the Bookmarks & History component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.
- CVE-2026-100819Critical
Sandbox escape due to incorrect boundary conditions in the XPCOM component. Fixed in multiple Firefox and Thunderbird versions.
- CVE-2026-100818Critical
Sandbox escape due to use-after-free in the Widget: Gtk component. Fixed in multiple Firefox and Thunderbird versions.
- CVE-2026-100811Critical
Sandbox escape due to use-after-free in the DOM: Core & HTML component. Fixed in multiple Firefox and Thunderbird versions.
- CVE-2026-100810Critical
Other issue in the DevTools component. This vulnerability was fixed in Thunderbird 157 and Firefox 157.
- CVE-2026-100804Critical
Sandbox escape due to use-after-free in the Preferences: Backend component. Fixed in Thunderbird 157 and Firefox 157.
- CVE-2026-100800Critical
Sandbox escape due to use-after-free in the Disability Access APIs component. Fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.
- CVE-2026-100794Critical
Vulnerability allows sandbox escape due to incorrect boundary conditions in the Internationalization component. It was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, and Firefox ESR 140.17.
- CVE-2026-100788Critical
Vulnerability related to an invalid pointer in the JavaScript: WebAssembly component. It was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, and Firefox ESR 140.17.
Original NVD description (English source)
Sandbox escape in the XUL component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS