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.

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploitation none

Automatable yes

Technical Impact partial

Affected Vendors & Products

Vendors Products
Mozilla
  • Firefox
  • Thunderbird

Configuration 1 [-]

OR cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

No data.

References
Link Providers
https://bugzilla.mozilla.org/show_bug.cgi?id=2060048 cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-74986 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-74986 cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-74/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-77/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-77/#CVE-2026-74986 cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-78/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-80/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-80/#CVE-2026-74986 cve-icon
History

Tue, 25 Aug 2026 16:30:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla thunderbird
CPEs cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
Vendors & Products Mozilla thunderbird

Fri, 21 Aug 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-501
References
Metrics threat_severity

None

 threat_severity

Low

Thu, 20 Aug 2026 18:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-200
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Tue, 18 Aug 2026 22:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-200
CWE-285

Tue, 18 Aug 2026 19:00:00 +0000

Type Values Removed Values Added
Description Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1. 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.
References

Tue, 18 Aug 2026 14:15:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla
Mozilla firefox
Vendors & Products Mozilla
Mozilla firefox

Tue, 18 Aug 2026 14:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-200
CWE-285

Tue, 18 Aug 2026 12:45:00 +0000

Type Values Removed Values Added
Description Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.
Title Site isolation issue in the CSS Parsing and Computation component
References
cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published: 2026-08-18T12:23:41.380Z

Updated: 2026-08-20T17:21:07.306Z

Reserved: 2026-08-17T11:59:20.279Z

Link: CVE-2026-74986

cve-icon Vulnrichment

Updated: 2026-08-20T15:47:36.311Z

cve-icon NVD

Status : Analyzed

Published: 2026-08-18T13:17:40.433

Modified: 2026-08-25T16:11:58.203

Link: CVE-2026-74986

cve-icon Redhat

Severity : Low

Publid Date: 2026-08-18T12:23:41Z

Links: CVE-2026-74986 - Bugzilla