CVE-2026-84129
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk10th percentile - higher than 10% of all known CVEs
Summary
The vulnerability concerns a site isolation issue in the DOM: Navigation component in Firefox and Thunderbird. The flaw was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Risk Assessment
The risk involves potential breach of site isolation, which could lead to unauthorized access to data or unintended actions in the context of another site.
Recommendation
It is recommended to update Firefox and Thunderbird to the patched versions (Firefox 155, Firefox ESR 153.2, Thunderbird 155, Thunderbird 153.2) as soon as possible.
Other vulnerabilities in Firefox
See all- CVE-2026-109755Critical
A vulnerability in the DOM: Content Processes component allows sandbox escape. It was fixed in Firefox 158 and Thunderbird 158.
- CVE-2026-109708Critical
Sandbox escape due to incorrect boundary conditions in the Networking component. The vulnerability was fixed in Firefox 158, Firefox ESR 153.5, and Thunderbird 158 and 153.5.
- CVE-2026-109707Critical
Sandbox escape due to use-after-free in the Networking component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
- CVE-2026-109705Critical
Sandbox escape, site isolation issue due to incorrect boundary conditions, use-after-free in the Networking component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
- CVE-2026-106016Critical
Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox 157.0.1 and Thunderbird 158.
- CVE-2026-100829Critical
Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.
- CVE-2026-100828Critical
Mitigation bypass in the Bookmarks & History component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.
- CVE-2026-100819Critical
Sandbox escape due to incorrect boundary conditions in the XPCOM component. Fixed in multiple Firefox and Thunderbird versions.
- CVE-2026-100818Critical
Sandbox escape due to use-after-free in the Widget: Gtk component. Fixed in multiple Firefox and Thunderbird versions.
- CVE-2026-100811Critical
Sandbox escape due to use-after-free in the DOM: Core & HTML component. Fixed in multiple Firefox and Thunderbird versions.
Original NVD description (English source)
Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS