Vulnerability in Mozilla Firefox
CVE-2025-4083
A process isolation vulnerability in Thunderbird 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 was fixed in Firefox 138, Firefox ESR 128.10, Firefox ESR 115.23, Thunderbird 138, and Thunderbird 128.10.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.005 (37.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 37th percentile — 37.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.000
Affected products
- Mozilla Firefox — versions 115.23, 128.10, 138
- Mozilla Thunderbird — versions 128.10, 138
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2025-28/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-29/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-30/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-31/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-32/ (Vendor Advisory)
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2025-4083?
- CVE-2025-4083 is a critical-severity vulnerability in Mozilla Firefox, classified under CWE-653. CVSS score: 9.1/10. Published 2025-04-29.
- How severe is CVE-2025-4083?
- Critical severity. CVSS v3 base score is 9.1 out of 10.
- Is CVE-2025-4083 known to be exploited?
- 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.