CVE-2026-109705

Name of the Vulnerable Software and Affected Versions Firefox versions prior to 158 Firefox ESR versions prior to 153.5 Thunderbird versions prior to 158 Thunderbird versions prior to 153.5

Description A use-after-free issue exists in the Networking component caused by incorrect boundary conditions. This leads to a sandbox escape and a site isolation failure, where site isolation is a security mechanism that ensures web content from different sites is processed in separate processes to prevent data theft.

Recommendations Update Firefox to version 158 or later. Update Firefox ESR to version 153.5 or later. Update Thunderbird to version 158 or later. Update Thunderbird to version 153.5 or later.