A race during concurrent delazification could have led to a use-after-free. This vulnerability was fixed in Firefox 135, Firefox ESR 115.20, Firefox ESR 128.7, Thunderbird 128.7, and Thunderbird 135.CreditsNils BarsReferenceshttps://bugzilla.mozilla.org/show_bug.cgi?id=1939710https://www.mozilla.org/security/advisories/mfsa2025-07/https://www.mozilla.org/security/advisories/mfsa2025-08/https://www.mozilla.org/security/advisories/mfsa2025-09/https://www.mozilla.org/security/advisories/mfsa2025-10/https://www.mozilla.org/security/advisories/mfsa2025-11/
