CVE-2026-109721

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 Incorrect boundary conditions exist within the Just-In-Time (JIT) component of the JavaScript Engine. JIT is a method of improving program performance by compiling code during execution rather than before.

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