Vulnerability in Mozilla Firefox
CVE-2026-4692
Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 10.0 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.005 (39.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 40th percentile — 39.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000
Affected products
- Mozilla Firefox — versions 115.34, 140.9, 149
- Mozilla Thunderbird — versions 140.9, 149
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2026-20/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-21/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-22/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-23/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-24/ (Vendor Advisory)
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-4692?
- CVE-2026-4692 is a critical-severity vulnerability in Mozilla Firefox, classified under CWE-653. CVSS score: 10.0/10. Published 2026-03-24.
- How severe is CVE-2026-4692?
- Critical severity. CVSS v3 base score is 10.0 out of 10.
- Is CVE-2026-4692 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.