Site Isolation Issue in Firefox Navigation Component
CVE-2026-16399

7.5HIGH

Key Information:

Vendor

Mozilla
Status
Firefox
Thunderbird
Vendor
CVE Published:
21 July 2026

What is CVE-2026-16399?

A site isolation issue has been identified in the DOM navigation component of the Firefox browser. This vulnerability could potentially allow unauthorized access to sensitive data across different sites. Mozilla has addressed this issue in the latest Firefox release, version 153, enhancing the browser's security features. Users are encouraged to update to the latest version to mitigate any associated risks.

Affected Version(s)

Firefox 153

Thunderbird 153

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2049981
https://www.mozilla.org/security/advisories/mfsa2026-68/
https://www.mozilla.org/security/advisories/mfsa2026-71/

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
High
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Yaqoub Aldurayhim
.