---
id: CVE-2025-40271
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  fs/proc: fix uaf in proc_readdir_de()

  Pde is erased from subdir rbtree through rb_erase(), but not set the node
  to EMPTY, which may result in uaf access
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  fs/proc: fix uaf in proc_readdir_de()

  Pde is erased from subdir rbtree through rb_erase(), but not set the node
  to EMPTY, which may result in uaf access.  We should us…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
published: '2025-12-06'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T19:10:00.173'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-40271'
references:
  - url: 'https://git.kernel.org/stable/c/03de7ff197a3d0e17d0d5c58fdac99a63cba8110'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/1d1596d68a6f11d28f677eedf6cf5b17dbfeb491'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/4cba73c4c89219beef7685a47374bf88b1022369'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/623bb26127fb581a741e880e1e1a47d79aecb6f8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/67272c11f379d9aa5e0f6b16286b9d89b3f76046'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6f2482745e510ae1dacc9b090194b9c5f918d774'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/895b4c0c79b092d732544011c3cecaf7322c36a1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c81d0385500446efe48c305bbb83d47f2ae23a50'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-253495.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - exploit-available
epss: 0.00455
epssPercentile: 0.37948
exploits:
  exploitdb: true
  github: 2
  githubRepos:
    - 'https://github.com/MadExploits/CVE-2025-40271'
    - 'https://github.com/kaleth4/CVE-2025-40271'
  checkedAt: '2026-10-15T19:26:21.050Z'
exploitAvailable: true
ingestedAt: '2026-10-15T19:25:46.331Z'
---

## Overview

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

fs/proc: fix uaf in proc_readdir_de()

Pde is erased from subdir rbtree through rb_erase(), but not set the node
to EMPTY, which may result in uaf access.  We should use RB_CLEAR_NODE()
set the erased node to EMPTY, then pde_subdir_next() will return NULL to
avoid uaf access.

We found an uaf issue while using stress-ng testing, need to run testcase
getdent and tun in the same time.  The steps of the issue is as follows:

1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current
   pde is tun3;

2) in the [time windows] unregister netdevice tun3 and tun2, and erase
   them from rbtree.  erase tun3 first, and then erase tun2.  the
   pde(tun2) will be released to slab;

3) continue to getdent process, then pde_subdir_next() will return
   pde(tun2) which is released, it will case uaf access.

CPU 0                                      |    CPU 1
-------------------------------------------------------------------------
traverse dir /proc/pid/net/dev_snmp6/      |   unregister_netdevice(tun->dev)   //tun3 tun2
sys_getdents64()                           |
  iterate_dir()                            |
    proc_readdir()                         |
      proc_readdir_de()                    |     snmp6_unregister_dev()
        pde_get(de);                       |       proc_remove()
        read_unlock(&proc_subdir_lock);    |         remove_proc_subtree()
                                           |           write_lock(&proc_subdir_lock);
        [time window]                      |           rb_erase(&root->subdir_node, &parent->subdir);
                                           |           write_unlock(&proc_subdir_lock);
        read_lock(&proc_subdir_lock);      |
        next = pde_subdir_next(de);        |
        pde_put(de);                       |
        de = next;    //UAF                |

rbtree of dev_snmp6
                        |
                    pde(tun3)
                     /    \
                  NULL  pde(tun2)

## Remediation

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