---
id: CVE-2026-63810
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  block: Avoid mounting the bdev pseudo-filesystem in userspace

  The bdev pseudo-filesystem is an internal kernel filesystem with which
  userspace should not interfere
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  block: Avoid mounting the bdev pseudo-filesystem in userspace

  The bdev pseudo-filesystem is an internal kernel filesystem with which
  userspace should not interfere. Un…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    3d3fcf23993bb756de2f912ab631cfdcc4746554
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    99cde0a7b1e98fd3970aabef1300918e91698dd5
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    1a02a5028bd6dead1f8503854ef3168d651cd417
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    197971e6ffc0a6356b2ba2b22beb42bc0f7e412d
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    3804e6de30ae7b053d53341d9d6944356cf23b40
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    717f721eb67d2dacd3ed5f7495aef2f442e84ce4
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    f73aa66dffcb8e61e78f01b56163ec16a15d06d2
  - Linux 2.6.12
published: '2026-07-19'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T09:18:17.710'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63810'
references:
  - url: 'https://git.kernel.org/stable/c/197971e6ffc0a6356b2ba2b22beb42bc0f7e412d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/1a02a5028bd6dead1f8503854ef3168d651cd417'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3804e6de30ae7b053d53341d9d6944356cf23b40'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3d3fcf23993bb756de2f912ab631cfdcc4746554'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/717f721eb67d2dacd3ed5f7495aef2f442e84ce4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/99cde0a7b1e98fd3970aabef1300918e91698dd5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f73aa66dffcb8e61e78f01b56163ec16a15d06d2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-019113.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00187
epssPercentile: 0.07396
ingestedAt: '2026-07-20T09:37:17.847Z'
---

## Overview

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

block: Avoid mounting the bdev pseudo-filesystem in userspace

The bdev pseudo-filesystem is an internal kernel filesystem with which
userspace should not interfere. Unregister it so that userspace cannot
even attempt to mount it.

This fixes a bug [1] that occurs when attempting to access files,
because the system call move_mount() uses pointers declared in the
inode_operations structure, which for the bdev pseudo-filesystem
are always equal to 0. `inode->i_op = &empty_iops;`

[1]

 BUG: kernel NULL pointer dereference, address: 0000000000000000
 #PF: supervisor instruction fetch in kernel mode
 #PF: error_code(0x0010) - not-present page
 PGD 23380067 P4D 23380067 PUD 23381067 PMD 0
 Oops: 0010 [#1] PREEMPT SMP KASAN NOPTI
 CPU: 2 PID: 17125 Comm: syz-executor.0 Not tainted 6.1.155-syzkaller-00350-g84221fde2681 #0
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
 RIP: 0010:0x0

 Call Trace:
 <TASK>
 lookup_open.isra.0+0x700/0x1180 fs/namei.c:3460
 open_last_lookups fs/namei.c:3550 [inline]
 path_openat+0x953/0x2700 fs/namei.c:3780
 do_filp_open+0x1c5/0x410 fs/namei.c:3810
 do_sys_openat2+0x171/0x4d0 fs/open.c:1318
 do_sys_open fs/open.c:1334 [inline]
 __do_sys_openat fs/open.c:1350 [inline]
 __se_sys_openat fs/open.c:1345 [inline]
 __x64_sys_openat+0x13c/0x1f0 fs/open.c:1345
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

## Remediation

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