CVE-2026-16375

Site isolation issue in the Networking: HTTP component

State: Published
Severity: 9.8 Critical
Published: Jul 21, 2026
Updated: Jul 22, 2026
Reserved: Jul 20, 2026

Description

Site isolation issue in the Networking: HTTP component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

Scores

CVSS	Score	Vector	Source
3.1	9.8 Critical	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H	CISA-ADP

Weaknesses

CWE-346 Origin Validation Error

Affected Products

Product	Versions
FirefoxMozilla	140.13 through 140.*Not affected 153 and laterNot affected
ThunderbirdMozilla	140.13 through 140.*Not affected 153 and laterNot affected

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2032140
https://www.mozilla.org/security/advisories/mfsa2026-68/
https://www.mozilla.org/security/advisories/mfsa2026-70/
https://www.mozilla.org/security/advisories/mfsa2026-71/
https://www.mozilla.org/security/advisories/mfsa2026-72/

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