CVE-2026-109708
CriticalCVSS 9.6Exploitation Probability (EPSS)
Low risk25th percentile - higher than 25% of all known CVEs
Summary
A sandbox escape vulnerability in the Networking component of Firefox and Thunderbird is caused by incorrect boundary conditions. It was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird 153.5, and Firefox ESR 115.44.
Risk Assessment
A sandbox escape can allow code execution outside the browser isolation boundary, significantly increasing the risk of system compromise via malicious web content. Organizations running vulnerable versions are exposed to privilege escalation and workstation compromise.
Recommendation
Update Firefox and Thunderbird to the fixed versions (Firefox 158, ESR 153.5, ESR 115.44, Thunderbird 158, 153.5). Prioritize workstations with internet access.
Other vulnerabilities in Firefox and Thunderbird Networking component
See all- CVE-2026-109707Critical
A use-after-free vulnerability in the Networking component of Firefox and Thunderbird enables a sandbox escape. It was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird 153.5, and Firefox ESR 115.44.
- CVE-2026-109705Critical
A vulnerability in the Networking component of Firefox and Thunderbird combines incorrect boundary conditions and use-after-free, leading to a sandbox escape and site isolation issue. It was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird 153.5, and Firefox ESR 115.44.
Original NVD description (English source)
Sandbox escape due to incorrect boundary conditions in the Networking component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, Thunderbird 153.5, and Firefox ESR 115.44.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS