An attacker can read 32‑bit values that are inadvertently written to the stack by a JIT‑compiled function. The read exposes data stored in those stack slots, potentially leaking sensitive runtime information. The vulnerability is categorized as CWE‑200 (Information Exposure) and CWE‑203 (Improper Assertion of Security-relevant Data).

Mozilla Firefox and Mozilla Thunderbird versions before 137 are affected. The fix is included in Firefox 137 and Thunderbird 137, so any release prior to those versions is potentially vulnerable.

The CVSS score is 6.5, indicating moderate severity. EPSS is below 1 %, showing a very low likelihood of exploitation at present. The vulnerability is not listed in the CISA KEV catalog, suggesting no publicly known exploits. The attack requires execution of malicious code that triggers a JIT‑compiled function, such as a crafted webpage or email attachment executed in the target application.