Use After Free in Mozilla Firefox
CVE-2026-12291
Use-after-free in the Networking: HTTP component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
Vulnerability class: Use-After-Free
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.004 (29.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 30th percentile — 29.6% 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: 0.004 · change: 0.000
Affected products
- Mozilla Firefox — versions 115.37, 140.12, 152
- Mozilla Thunderbird — versions 140.12, 152
Weakness classification (CWE)
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2026-57/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-58/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-59/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-60/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-61/ (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-2026-12291?
- CVE-2026-12291 is a high-severity vulnerability in Mozilla Firefox, classified under Use After Free. CVSS score: 8.8/10. Published 2026-06-16.
- How severe is CVE-2026-12291?
- High severity. CVSS v3 base score is 8.8 out of 10.