CVE-2026-109707
CriticalCVSS 9.6Exploitation Probability (EPSS)
Low risk24th percentile - higher than 24% of all known CVEs
Summary
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.
Risk Assessment
Exploiting the use-after-free can lead to arbitrary code execution and escape from the sandbox, risking full compromise of the user's system. The risk is especially high when browsing untrusted sites.
Recommendation
Immediately update Firefox and Thunderbird to the fixed versions listed in the advisory. Verify versions across all workstations and mail servers.
Other vulnerabilities in Firefox and Thunderbird Networking component
See all- CVE-2026-109708Critical
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.
- 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 use-after-free 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