CVE-2026-16359
CVE-2026-16359 is a critical vulnerability (CVSS 9.1) in the Audio/Video GMP component of Firefox and Thunderbird, caused by incorrect boundary conditions that could allow an attacker to execute arbitrary code. The issue was resolved in Firefox 153, Firefox ESR 115.38 and 140.13, Thunderbird 153, and Thunderbird 140.13.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Users of Firefox, Firefox ESR, Thunderbird, and Thunderbird ESR.
Real-world impact
An attacker could potentially execute arbitrary code on a victim's system by exploiting the boundary condition flaw.
Why this severity
With a CVSS base score of 9.1, the vulnerability is rated critical due to its network‑attack vector, low complexity, and high impact on confidentiality and integrity.
What to do about it
- 01Upgrade Firefox to version 153.
- 02Upgrade Firefox ESR to version 115.38 (if using the ESR 115 branch) or version 140.13 (if using the ESR 140 branch).
- 03Upgrade Thunderbird to version 153.
- 04Upgrade Thunderbird ESR to version 140.13.
NVD-referenced vendor advisory
Timeline
- Jul 21, 2026 · 12d agoPublishedDisclosed and added to the National Vulnerability Database.
- Jul 21, 2026 · 11d 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
- mozilla.org/security/advisories/mfsa202…vendor advisory