Site isolation issue in the WebExtensions component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, 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 High

Availability Impact None

User Interaction Required

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploitation none

Automatable no

Technical Impact total

Affected Vendors & Products

Vendors Products
Mozilla
  • Firefox

No data.

No data.

References
Link Providers
https://bugzilla.mozilla.org/show_bug.cgi?id=2049148 cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-74960 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-74960 cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-74/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-76/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-76/#CVE-2026-74960 cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-77/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-78/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-79/ cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-79/#CVE-2026-74960 cve-icon
https://www.mozilla.org/security/advisories/mfsa2026-80/ cve-icon cve-icon
History

Fri, 21 Aug 2026 20:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-284
CWE-346
Metrics cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}

 ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N'}

Fri, 21 Aug 2026 18:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-200
CWE-264

Wed, 19 Aug 2026 00:15:00 +0000

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

None

 cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}

threat_severity

Moderate

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

Type Values Removed Values Added
Description Site isolation issue in the WebExtensions component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1. Site isolation issue in the WebExtensions component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
References

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

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

Tue, 18 Aug 2026 14:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-200
CWE-264

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

Type Values Removed Values Added
Description Site isolation issue in the WebExtensions component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.
Title Site isolation issue in the WebExtensions component
References
cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published: 2026-08-18T12:23:31.590Z

Updated: 2026-08-21T20:00:22.910Z

Reserved: 2026-08-17T11:58:22.429Z

Link: CVE-2026-74960

cve-icon Vulnrichment

Updated: 2026-08-21T20:00:17.199Z

cve-icon NVD

Status : Undergoing Analysis

Published: 2026-08-18T13:17:33.170

Modified: 2026-08-21T20:16:41.817

Link: CVE-2026-74960

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-08-18T12:23:31Z

Links: CVE-2026-74960 - Bugzilla