CVE-2026-46243

A privilege escalation vulnerability was found in the Linux kernel's CIFS client implementation. This could allow a local attacker to impersonate other users, bypass authentication in SMB mount operations, and potentially gain unauthorized access to network file shares or escalate privileges.

This issue is classified as Important severity primarily because a low-privileged local user can achieve full privilege escalation to root without any user interaction. The attack requires local access, which prevents remote exploitation and is the primary factor keeping the rating at Important rather than Critical.

Exploitation requires three components to be present on the system: the cifs kernel module (loaded or loadable), the cifs-utils package with its default cifs.spnego request-key rule, and the ability to create unprivileged user and mount namespaces. All three must be present for the attack chain to succeed. Environments that do not use SMB/CIFS file shares or Active Directory integration are unlikely to have cifs-utils installed, reducing their exposure.

In OpenShift Container Platform 4, this flaw is rated Low. The default restricted-v2 Security Context Constraint (SCC) sets allowPrivilegeEscalation: false on all pods, which causes the kernel to ignore setuid file bits, preventing privilege escalation. Under non-default SCCs such as anyuid that permit privilege escalation, the vulnerability is constrained by PID and mount namespace isolation to the container's own filesystem. An attacker would only be able to escalate privileges within the container, not on the host or across pods.

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.

See the security bulletin for a detailed mitigation procedure.