---
id: CVE-2026-97564
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  smb: client: reject userspace cifs.idmap descriptions

  cifs.idmap key descriptions carry authority-bearing fields (owner and
  group SIDs and uid/gid values in "os:"/"gs:…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  smb: client: reject userspace cifs.idmap descriptions

  cifs.idmap key descriptions carry authority-bearing fields (owner and
  group SIDs and uid/gid values in "os:"/"gs:…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 4d79dba0e00749fa40de8ef13a9b85ce57a1603b <
    e5964064e3fbe6325893408faff08ca33de0e2c3
  - >-
    Linux >= 4d79dba0e00749fa40de8ef13a9b85ce57a1603b <
    96751028c0d4dec785709ea3eb0ab38a4f2ded96
  - >-
    Linux >= 4d79dba0e00749fa40de8ef13a9b85ce57a1603b <
    1d3b24b16a0b013792e8f1e3ed060f0b46f537d1
  - >-
    Linux >= 4d79dba0e00749fa40de8ef13a9b85ce57a1603b <
    d9d7eeb0cea5b55b82888f443622fd8d4ee064f3
  - Linux 3.0
published: '2026-09-25'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T11:17:07.007'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-97564'
references:
  - url: 'https://git.kernel.org/stable/c/1d3b24b16a0b013792e8f1e3ed060f0b46f537d1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/96751028c0d4dec785709ea3eb0ab38a4f2ded96'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d9d7eeb0cea5b55b82888f443622fd8d4ee064f3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e5964064e3fbe6325893408faff08ca33de0e2c3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-25T11:06:38.914Z'
---

## Overview

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

smb: client: reject userspace cifs.idmap descriptions

cifs.idmap key descriptions carry authority-bearing fields (owner and
group SIDs and uid/gid values in "os:"/"gs:"/"oi:"/"gi:" form) that the
cifs.idmap upcall helper treats as kernel-originating inputs.  Unlike
its sibling cifs.spnego, the cifs.idmap key type has no vet_description
hook, so userspace can create keys of this type through
request_key(2)/add_key(2) and supply those fields without CIFS origin.
A request_key(2) call with a non-NULL callout then drives a root
usermodehelper upcall (/sbin/request-key -> cifs.idmap) that consumes
the unvetted description in root context.

Only accept cifs.idmap descriptions while CIFS is using its private
root_cred to request the key.  id_to_sid()/sid_to_id() already run
under override_creds(root_cred), so the kernel-originated path is
unaffected.

This mirrors commit 3da1fdf4efbc ("smb: client: reject userspace
cifs.spnego descriptions"), which applied the same restriction to
cifs.spnego.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.