CVE-2026-16353
A critical flaw in Firefox and Thunderbird’s WebIDL bindings can let attackers crash or take control of the browser. The issue was fixed in Firefox 153, ESR 115.38, ESR 140.13, Thunderbird 153, and Thunderbird 140.13. Users should update to these or newer releases.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Firefox and Thunderbird users running versions older than Firefox 153, Firefox ESR 115.38, Firefox ESR 140.13, Thunderbird 153, or Thunderbird 140.13.
Real-world impact
An attacker could exploit the vulnerability to crash the browser or execute arbitrary code, potentially compromising the user’s system or data.
Why this severity
The CVSS score is high because the flaw requires no authentication, has no user interaction, and grants full compromise of confidentiality, integrity, and availability.
What to do about it
- 01Upgrade Firefox to version 153 or later, or to ESR 115.38 or ESR 140.13.
- 02Upgrade Thunderbird to version 153 or later, or to ESR 140.13.
- 03Restart the browser after the update to ensure the new code is loaded.
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
- mozilla.org/security/advisories/mfsa202…vendor advisory