CVE-2025-1012: A race during concurrent delazification could have led to a use-after-free
Source GCVE Database
Not known to be exploited · CVSS 9.8 Critical.
Data as of 29 Oct 2026, 22:52 UTC
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 4 Feb 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
Description
A race during concurrent delazification could have led to a use-after-free. This vulnerability affects Firefox < 135, Firefox ESR < 115.20, Firefox ESR < 128.7, Thunderbird < 128.7, and Thunderbird < 135.
References
- nvd.nist.gov/vuln/detail/CVE-2025-1012 (opens in a new tab)
- bugzilla.mozilla.org/show_bug.cgi?id=1939710 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/02/msg00005.html (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/02/msg00006.html (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-07 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-08 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-09 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-10 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-11 (opens in a new tab)