CVE-2026-64137

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

smb: client: require net admin for CIFS SWN netlink

CIFS_GENL_CMD_SWN_NOTIFY 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

RESOURCE_CHANGE or CLIENT_MOVE notifications to the in-kernel witness

handler.

The same family exposes CIFS_GENL_MCGRP_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 CAP_NET_ADMIN for incoming SWN_NOTIFY commands with

GENL_ADMIN_PERM, and require CAP_NET_ADMIN over the network namespace for

joining the SWN multicast group with GENL_MCAST_CAP_NET_ADMIN. The

cifs.witness service runs with the privileges needed for both operations.