CVE & CISA-KEV CatalogNVD
CVE-2026-4691
CRITICAL9.8
CVSS v3
Description
Use-after-free in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
CVSS v3 Vector
Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploit Intelligence
0.49%probability of exploitation in 30 days
38thpercentile
Low risk: more likely to be exploited than 38% of all known CVEs.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2017512
- https://www.mozilla.org/security/advisories/mfsa2026-20/
- https://www.mozilla.org/security/advisories/mfsa2026-21/
- https://www.mozilla.org/security/advisories/mfsa2026-22/
- https://www.mozilla.org/security/advisories/mfsa2026-23/
- https://www.mozilla.org/security/advisories/mfsa2026-24/
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Start freeThis product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-13.