CVE-2026-64379

A flaw was found in the Linux kernel's Server Message Block (SMB) client. When processing server-provided file mode information, the system incorrectly applies these modes without proper security masking. This can result in unintended file permissions, potentially allowing unauthorized access to files or directories.

This vulnerability is rated as Moderate severity for Red Hat Enterprise Linux because successful exploitation requires mounting a CIFS share using the non-default modefromsid option against an untrusted or compromised SMB server. Under default configurations, CIFS mounts do not enable this behavior, significantly restricting exposure. While malformed permission attributes from the server can cause improper file access permissions on the mounted filesystem, the blast radius is confined to the specific mount without compromising the host kernel.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.