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9.8
Firefox and Thunderbird: Malicious Web Pages Can Access Local Files
CVE-2026-2790
Summary
Certain versions of Firefox and Thunderbird allow malicious web pages to access local files, which could lead to data theft or other security risks. This affects users who haven't updated to the latest versions. To fix this, update to the latest version of Firefox or Thunderbird to ensure you have the latest security patches.
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
Same-origin policy bypass in the Networking: JAR component. This vulnerability affects Firefox < 148, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
Original description
Same-origin policy bypass 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-346
- https://bugzilla.mozilla.org/show_bug.cgi?id=2008426 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