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5.4
Firefox and Thunderbird: Malicious WebAssembly Code Can Crash Browser
CVE-2026-2804
Summary
Firefox and Thunderbird versions less than 148 contain a bug that can cause the browser to crash or become unresponsive when it encounters malicious WebAssembly code. This can lead to a denial-of-service condition, where the browser is unable to function properly. To fix this issue, update to version 148 or later.
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 | thunderbird | <= 148.0 | – |
Original title
Use-after-free in the JavaScript: WebAssembly component. This vulnerability affects Firefox < 148 and Thunderbird < 148.
Original description
Use-after-free in the JavaScript: WebAssembly component. This vulnerability affects Firefox < 148 and Thunderbird < 148.
nvd CVSS3.1
5.4
Vulnerability type
CWE-416
Use After Free
- https://bugzilla.mozilla.org/show_bug.cgi?id=2013584 Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2026-13/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-16/ Vendor Advisory
Published: 24 Feb 2026 · Updated: 12 Mar 2026 · First seen: 6 Mar 2026