What’s Vulnerable › Vulnerabilities

CVE-2026-16399: Site isolation issue in the DOM: Navigation component

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-21 · updated 2026-10-24
• Weakness: CWE-346

Description

Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.

Affected products

• Mozilla Firefox: before 153.0.0 — fixed in 153.0.0
• Mozilla Thunderbird: before 153.0 — fixed in 153.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 153.0.0; Mozilla Thunderbird 153.0. Check the vendor advisory for mitigations.

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/

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