During Ion compilation, a Garbage Collection could have resulted in a use-after-free condition, allowing an attacker to write two NUL bytes, and cause a potentially exploitable crash. This vulnerability affects Firefox < 118, Firefox ESR < 115.3, and Thunderbird < 115.3.
https://www.mozilla.org/security/advisories/mfsa2023-43/
https://www.mozilla.org/security/advisories/mfsa2023-42/
https://www.mozilla.org/security/advisories/mfsa2023-41/
https://www.debian.org/security/2023/dsa-5513
https://www.debian.org/security/2023/dsa-5506
https://lists.debian.org/debian-lts-announce/2023/10/msg00015.html
https://lists.debian.org/debian-lts-announce/2023/09/msg00034.html