Vulnerability in Mozilla Firefox
CVE-2026-75874
Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154, Thunderbird 154, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 140.15, and Thunderbird 153.2.
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 (37.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 37th percentile — 37.3% 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
Weakness classification (CWE)
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2026-74/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-78/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-83/
- www.mozilla.org/security/advisories/mfsa2026-84/
- www.mozilla.org/security/advisories/mfsa2026-85/
- www.mozilla.org/security/advisories/mfsa2026-87/
- www.mozilla.org/security/advisories/mfsa2026-88/
Frequently asked questions
- What is CVE-2026-75874?
- CVE-2026-75874 is a critical-severity vulnerability in Mozilla Firefox, classified under Protection Mechanism Failure. CVSS score: 10.0/10. Published 2026-08-18.
- How severe is CVE-2026-75874?
- Critical severity. CVSS v3 base score is 10.0 out of 10.