Assuming a controlled failed memory allocation, an attacker could have caused a use-after-free, leading to a potentially exploitable crash. This vulnerability affects Firefox < 134, Firefox ESR < 128.6, Firefox ESR < 115.19, Thunderbird < 134, and Thunderbird ESR < 128.6.
https://www.mozilla.org/security/advisories/mfsa2025-05/
https://www.mozilla.org/security/advisories/mfsa2025-04/
https://www.mozilla.org/security/advisories/mfsa2025-03/
https://www.mozilla.org/security/advisories/mfsa2025-02/