CVE-2026-6766 describes a security vulnerability caused by incorrect boundary conditions in the NSS Libraries component within Mozilla Firefox. NSS is a set of libraries designed to support cross-platform development of security-enabled client and server applications. The vulnerability was addressed and fixed in Firefox 150 and Firefox ESR 140.10. The Mozilla security advisories list this vulnerability among several others fixed in these versions, with an impact rating of moderate. No CVSS score is provided, but the vendor advisory confirms the availability of an official fix.

The vulnerability could allow potential security issues due to improper boundary checks in the NSS Libraries component. While the exact exploitation details are not provided, the impact is rated moderate by Mozilla. This suggests that the vulnerability could lead to security concerns such as memory corruption or other unintended behavior but is not classified as critical or high impact. There are no known exploits in the wild at the time of publication.

Mozilla has released official fixes for this vulnerability in Firefox 150 and Firefox ESR 140.10. Users and administrators should update affected Firefox installations to these versions or later to remediate the vulnerability. Since this is not a cloud service, patching the client software is required. There are no vendor advisories indicating that no action is required or that the issue is already mitigated without patching.