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9.6

Firefox and Thunderbird can bypass sandbox

CVE-2026-109755 · published 2 days ago
Summary

A flaw in the web page handling component of Firefox and Thunderbird could let a malicious site break out of its isolated environment and run code on the user’s computer. This could expose personal data or allow unwanted actions. Updating to the latest version of each application resolves the issue.

What to do

The CVE record does not list a fixed version. Check the vendor's site or the advisory links below - a fix may already be released.

Affected software
VendorProductAffected versions
mozilla firefox All versions
mozilla thunderbird All versions
Original advisory text
Sandbox escape in the DOM: Content Processes component
Sandbox escape in the DOM: Content Processes component. This vulnerability was fixed in Firefox 158 and Thunderbird 158.
References
Severity
9.6 Critical
Exploitation
<1% chance of attack within 30 days
Type
CWE-693Protection Mechanism Failure
Timeline
Published13 Oct 2026
Updated15 Oct 2026
First seen13 Oct 2026
Sources
CVE-2026-109755 · NVD
CVE-2026-109755 · MITRE
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