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9.8
Firefox and Thunderbird: Malicious Web Content Can Crash Browser
CVE-2026-2767
Summary
A bug in Firefox and Thunderbird allows attackers to crash the browser or steal data by using a malicious website. This affects Firefox versions older than 148 and Thunderbird versions older than 140.8. To protect yourself, update to the latest version of Firefox or Thunderbird.
What to do
No fix is available yet. Check with your software vendor for updates.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| mozilla | firefox | <= 148.0 | – |
| mozilla | firefox | <= 140.8.0 | – |
| mozilla | thunderbird | <= 140.8.0 | – |
| mozilla | thunderbird | <= 148.0 | – |
Original title
Use-after-free in the JavaScript: WebAssembly component. This vulnerability affects Firefox < 148, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
Original description
Use-after-free in the JavaScript: WebAssembly component. This vulnerability affects Firefox < 148, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
nvd CVSS3.1
9.8
Vulnerability type
CWE-416
Use After Free
- https://bugzilla.mozilla.org/show_bug.cgi?id=2013741 Issue Tracking Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2026-13/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-15/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-16/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-17/ Vendor Advisory
Published: 24 Feb 2026 · Updated: 12 Mar 2026 · First seen: 6 Mar 2026