CVE-2026-74986: mozilla firefox, mozilla thunderbird

CVSS 9.1 (critical) · published 2026-08-18

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.

Affected products (NVD): mozilla firefox, mozilla thunderbird

Fixed in (NVD): 153.1.0

Weakness: CWE-200

Source: NVD CVE-2026-74986

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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