CVE-2026-64137

In the Linux kernel, the following vulnerability has been resolved:

smb: client: require net admin for CIFS SWN netlink

CIFSGENLCMDSWNNOTIFY is the userspace witness-notify command. The intended sender is the cifs.witness helper, but the generic-netlink operation currently has no capability flag, so any local process can send RESOURCECHANGE or CLIENTMOVE notifications to the in-kernel witness handler.

The same family exposes CIFSGENLMCGRP_SWN without multicast-group capability flags. Register messages sent to that group include the witness registration id and, for NTLM-authenticated mounts, the username, domain, and password attributes copied from the CIFS session. An unprivileged local process should not be able to join that group and receive those messages.

Require CAPNETADMIN for incoming SWNNOTIFY commands with GENLADMINPERM, and require CAPNETADMIN over the network namespace for joining the SWN multicast group with GENLMCASTCAPNET_ADMIN. The cifs.witness service runs with the privileges needed for both operations.