CVE-2026-16369
An integer overflow in the WebAssembly component of Firefox and Thunderbird can allow attackers to run arbitrary code. The flaw is in the JavaScript engine and can be triggered remotely over the network. It is considered critical because it requires no user interaction or special privileges.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Firefox and Thunderbird browsers, including all versions prior to 153 and ESR 140.13.
Real-world impact
An attacker could execute arbitrary code, potentially taking full control of the victim’s system.
Why this severity
The CVSS score of 9.8 reflects that the vulnerability can be exploited over the network with low effort, requires no privileges or user interaction, and compromises confidentiality, integrity, and availability.
What to do about it
- 01Update Firefox to version 153 or later, or to Firefox ESR 140.13 or later.
- 02Update Thunderbird to version 153 or later, or to Thunderbird ESR 140.13 or later.
- 03Restart the browsers.
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