An attacker could exploit a use‑after‑free flaw in the browser’s layout engine, corrupting memory during the rendering of web content. This type of memory corruption can lead to arbitrary code execution if the attacker can craft content that triggers the vulnerable path.

Mozilla Firefox versions earlier than 159 and Mozilla Thunderbird versions earlier than 159 are vulnerable. Any user running these older builds may be impacted if malicious or crafted web content is viewed.

Knowledge of the flaw is publicly documented but no exploit score is available and it is not listed in the CISA KEV catalog, suggesting that widespread exploitation at this time is unlikely. The most plausible attack vector involves delivering tailored web pages that force the layout engine to operate on freed memory. Absent an official containment policy, the risk remains tied to the likelihood that attackers can successfully trigger the layout process on affected systems.