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Vulnerability record · CVE-2026-64137 · published 19 July 2026

CVE-2026-64137: Linux kernel vulnerability

Linux · Linux Kernel

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.

7.8 CVSS 3.1 High EPSS 0.18% · top 93.6%
7.8CVSS 3.1 base score
0.18%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
7References
13 Aug 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://git.kernel.org/stable/c/969bc6370334a5b4720c5470783295d6484bbc95 Patch
https://git.kernel.org/stable/c/9919021a3b7974ae66a5f9915e3a48c10cfd409b Patch
https://git.kernel.org/stable/c/9cf7eb8919344932f909b2fac76296f7656fda8d Patch
https://git.kernel.org/stable/c/a3238b09c58f323e40743ce174cd0ab81b5c09ed Patch
https://git.kernel.org/stable/c/a8d17d22db591099519a89f14dd24810daba74c3 Patch
https://git.kernel.org/stable/c/c2397b93fbb6f44a788fff30f99be2c20cc5e50f Patch
https://git.kernel.org/stable/c/d1ebfce2c1d161186a82e77590bf7da2ea1bce91 Patch

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Source: NIST National Vulnerability Database (record CVE-2026-64137), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.