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10.0
Firefox, Thunderbird: Attackers Can Escape Browser's Protective Sandbox
CVE-2026-2778
Summary
A security issue affects old versions of Firefox and Thunderbird, potentially allowing malicious code to escape the browser's protective sandbox and access sensitive information. This means that attackers could potentially steal data or take control of the user's system. Users should update to the latest version of their browser or email client to fix this 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 | <= 115.33.0 | – |
| mozilla | firefox | <= 148.0 | – |
| mozilla | firefox | > 128.0 , <= 140.8.0 | – |
| mozilla | thunderbird | <= 140.8.0 | – |
| mozilla | thunderbird | <= 148.0 | – |
Original title
Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Th...
Original description
Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
nvd CVSS3.1
10.0
Vulnerability type
CWE-119
Buffer Overflow
- https://bugzilla.mozilla.org/show_bug.cgi?id=2016358 Issue Tracking Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2026-13/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-14/ 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