---
id: CVE-2026-97926
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ufs: validate cylinder group metadata before caching it

  ufs_read_cylinder() copies the cylinder group index and the rotor
  positions straight from the on-disk group and…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ufs: validate cylinder group metadata before caching it

  ufs_read_cylinder() copies the cylinder group index and the rotor
  positions straight from the on-disk group and…
severity: high
cvss: 7
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    5902a95066883cf96fa15b2680694fc5dd0c7d11
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    87b12dc360a002eb2d498aa4f01e84347019612d
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    abde9eb33106850dfa367ad3965d3588bb8558d5
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    c9d263be26806d388129fab8c6904bed197fc6af
  - Linux 2.6.12
published: '2026-09-25'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T15:18:02.327'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-97926'
references:
  - url: 'https://git.kernel.org/stable/c/5902a95066883cf96fa15b2680694fc5dd0c7d11'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/87b12dc360a002eb2d498aa4f01e84347019612d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/abde9eb33106850dfa367ad3965d3588bb8558d5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c9d263be26806d388129fab8c6904bed197fc6af'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-25T11:06:38.887Z'
---

## Overview

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

ufs: validate cylinder group metadata before caching it

ufs_read_cylinder() copies the cylinder group index and the rotor
positions straight from the on-disk group and caches them without any
check:

	ucpi->c_cgx    = fs32_to_cpu(sb, ucg->cg_cgx);
	ucpi->c_rotor  = fs32_to_cpu(sb, ucg->cg_rotor);
	ucpi->c_frotor = fs32_to_cpu(sb, ucg->cg_frotor);
	ucpi->c_irotor = fs32_to_cpu(sb, ucg->cg_irotor);

They are then used as indices during allocation and free:

  - c_cgx indexes the cylinder summary array as
    UFS_SB(sb)->fs_cs(ucpi->c_cgx), so a value past s_ncg writes a 32
    bit count outside the s_csp allocation.

  - c_frotor becomes a bitmap scan start, start = c_frotor >> 3, and
    then length = ((s_fpg + 7) >> 3) - start. A start beyond the block
    bitmap wraps the unsigned length to a huge value, so ubh_scanc()
    walks far past the cylinder group buffers. c_irotor drives the
    inode bitmap the same way.

A crafted image can set any of these freely, turning an ordinary
allocation into an out of bounds access.

Reject a cylinder group whose recorded index does not match the group
being read, or whose rotors fall outside the group, before the metadata
is cached. Valid filesystems keep cg_cgx equal to the group number and
the rotors within the group, so only malformed images are rejected.

## Remediation

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