CVE-2026-100766

MediumCVSS 4.3

Published: 29/09/2026(UTC)Updated: 30/09/2026(UTC)Translated: 01/10/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Low risk

0.27%

17th percentile - higher than 17% of all known CVEs

Summary

Information disclosure in the Networking: JAR component. This vulnerability was fixed in multiple Firefox and Thunderbird versions.

Risk Assessment

May lead to disclosure of sensitive user or system data, increasing the risk of attacks.

Recommendation

Update Firefox and Thunderbird to the latest patched versions.

Other vulnerabilities in Firefox

See all

CVE-2026-109778High
A privilege escalation vulnerability in the WebExtensions component. It was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
CVE-2026-109756High
A privilege escalation vulnerability in the DOM: Navigation component. It was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
CVE-2026-109709High
An information disclosure and privilege escalation vulnerability in the Security: Process Sandboxing component. It was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 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.

Original NVD description (English source)

Information disclosure in the Networking: JAR component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS