CVE-2026-16371
CVE-2026-16371 is a critical privilege‑escalation flaw in the DOM Navigation component of Firefox and Thunderbird. An attacker with network access could exploit it to gain full control of the affected software. The issue was resolved in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird ESR 140.13.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Firefox, Firefox ESR, Thunderbird, and Thunderbird ESR (specific versions listed in the fix).
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
The CVSS v3.1 base score is 9.8 (Critical) due to network‑adjacent attack vector, low attack 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 Firefox ESR to version 140.13 or later.
- 03Upgrade Mozilla Thunderbird to version 153 or later.
- 04Upgrade Mozilla Thunderbird ESR to version 140.13 or later.
NVD-referenced vendor advisory
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
- mozilla.org/security/advisories/mfsa202…vendor advisory
- mozilla.org/security/advisories/mfsa202…vendor advisory