Firefox stemmed · Process Isolation Vulnerability
Source GCVE Database
Not known to be exploited · CVSS 9.1 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:NExploitation evidence
Disclosed: evidence found.
CVE published 29 Apr 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 process isolation vulnerability in Firefox stemmed from improper handling of javascript: URIs, which could allow content to execute in the top-level document's process instead of the intended frame, potentially enabling a sandbox escape. This vulnerability affects Firefox < 138, Firefox ESR < 128.10, Firefox ESR < 115.23, Thunderbird < 138, and Thunderbird ESR < 128.10.
References
- nvd.nist.gov/vuln/detail/CVE-2025-4083 (opens in a new tab)
- bugzilla.mozilla.org/show_bug.cgi?id=1958350 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/05/msg00024.html (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-28 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-29 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-30 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-31 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-32 (opens in a new tab)