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9.8
Firefox and Thunderbird: Malicious Website Can Steal User Data
CVE-2026-2779
Summary
The Firefox and Thunderbird browsers have a security issue that could allow a malicious website to access sensitive user data. This affects older versions of the browsers, and users should update to the latest version to protect themselves. Updating to the latest version will fix the issue.
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 | <= 140.8.0 | – |
| mozilla | firefox | <= 148.0 | – |
| mozilla | thunderbird | <= 140.8.0 | – |
| mozilla | thunderbird | <= 148.0 | – |
Original title
Incorrect boundary conditions in the Networking: JAR component. This vulnerability affects Firefox < 148, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
Original description
Incorrect boundary conditions in the Networking: JAR component. This vulnerability affects Firefox < 148, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
nvd CVSS3.1
9.8
Vulnerability type
CWE-119
Buffer Overflow
- https://bugzilla.mozilla.org/show_bug.cgi?id=1164141 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