CVE-2026-16366
CVE-2026-16366 is a critical privilege‑escalation flaw in the DOM Navigation component of Mozilla Firefox and Thunderbird. An attacker with network access can exploit it to gain full control of the affected software. The issue was resolved in Firefox 153 and Thunderbird 153.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Mozilla Firefox and Thunderbird (specific versions not listed in CPE data).
Real-world impact
Successful exploitation could allow an attacker to execute arbitrary code with the privileges of the application, leading to complete compromise of the user's system.
Why this severity
CVSS v3.1 base score 9.8 (Critical) reflects attack vector network, low complexity, no privileges or user interaction required, and high impact on confidentiality, integrity, and availability.
What to do about it
- 01Upgrade Mozilla Firefox to version 153 or later.
- 02Upgrade Mozilla Thunderbird to version 153 or later.
- 03Restart the browsers after upgrading to ensure the patched version is running.
NVD-referenced vendor advisory (fix mentioned in NVD description)
Timeline
- Jul 21, 2026 · 12d agoPublishedDisclosed and added to the National Vulnerability Database.
- Jul 23, 2026 · 10d agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.
- Jul 24, 2026 · 9d agoAdvisory updatedThe NVD record was last revised.
How it’s attacked
References & advisories
- bugzilla.mozilla.org/show_bug.cgipermissions required
- mozilla.org/security/advisories/mfsa202…vendor advisory
- mozilla.org/security/advisories/mfsa202…vendor advisory