CVE-2026-74986

9.1 criticalEPSS 0.6%

Critical (9.1) in mozilla. EPSS 0.6% chance of exploitation in the next 30 days.

Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.

Severity

CVSS 3.1

9.1 critical

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

EPSS: 0.6% chance of exploitation in the next 30 days; higher than 46% of CVEs (scores of 2026-10-31)
CWE: CWE-200
Published: 2026-08-18
Modified: 2026-08-25
Record from: the NVD, synced 2026-10-19

Affected

mozilla:firefox
mozilla:thunderbird

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2060048
https://www.mozilla.org/security/advisories/mfsa2026-74/
https://www.mozilla.org/security/advisories/mfsa2026-77/
https://www.mozilla.org/security/advisories/mfsa2026-78/
https://www.mozilla.org/security/advisories/mfsa2026-80/

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