Linux Kernel up to 6.18.12 sb_set_blocksize return value

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5.4$0-$5k0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.18.12. It has been declared as critical. Affected is the function sb_set_blocksize. The manipulation results in return value. This vulnerability is reported as CVE-2026-23238. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.18.12. Affected is the function sb_set_blocksize. The manipulation with an unknown input leads to a return value vulnerability. CWE is classifying the issue as CWE-252. The product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions. The impact remains unknown. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: romfs: check sb_set_blocksize() return value romfs_fill_super() ignores the return value of sb_set_blocksize(), which can fail if the requested block size is incompatible with the block device's configuration. This can be triggered by setting a loop device's block size larger than PAGE_SIZE using ioctl(LOOP_SET_BLOCK_SIZE, 32768), then mounting a romfs filesystem on that device. When sb_set_blocksize(sb, ROMBSIZE) is called with ROMBSIZE=4096 but the device has logical_block_size=32768, bdev_validate_blocksize() fails because the requested size is smaller than the device's logical block size. sb_set_blocksize() returns 0 (failure), but romfs ignores this and continues mounting. The superblock's block size remains at the device's logical block size (32768). Later, when sb_bread() attempts I/O with this oversized block size, it triggers a kernel BUG in folio_set_bh(): kernel BUG at fs/buffer.c:1582! BUG_ON(size > PAGE_SIZE); Fix by checking the return value of sb_set_blocksize() and failing the mount with -EINVAL if it returns 0.

The weakness was disclosed by the superblock. The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2026-23238 since 01/13/2026. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 06/24/2026).

The vulnerability scanner Nessus provides a plugin with the ID 301099 (Linux Distros Unpatched Vulnerability : CVE-2026-23238), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.10.251, 5.15.201, 6.1.164, 6.6.127, 6.12.74 or 6.18.13 eliminates this vulnerability. Applying the patch a381f0f61b35c8894b0bd0d6acef2d8f9b08b244/f2521ab1f63a8c244f06a080319e5ff9a2e1bd95/2c5829cd8fbbc91568c520b666898f57cdcb8cf6/cbd9931e6456822067725354d83446c5bb813030/9b203b8ddd7359270e8a694d0584743555128e2c/4b71ad7676564a94ec5f7d18298f51e8ae53db73/ab7ad7abb3660c58ffffdf07ff3bb976e7e0afa0 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (301099), EUVD (EUVD-2026-9410) and CERT Bund (WID-SEC-2026-0614). Once again VulDB remains the best source for vulnerability data.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • Microsoft Azure Linux
  • Open Source Linux Kernel
  • IBM QRadar SIEM

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.4

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Return value
CWE: CWE-252 / CWE-253
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 301099
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-23238

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.10.251/5.15.201/6.1.164/6.6.127/6.12.74/6.18.13
Patch: a381f0f61b35c8894b0bd0d6acef2d8f9b08b244/f2521ab1f63a8c244f06a080319e5ff9a2e1bd95/2c5829cd8fbbc91568c520b666898f57cdcb8cf6/cbd9931e6456822067725354d83446c5bb813030/9b203b8ddd7359270e8a694d0584743555128e2c/4b71ad7676564a94ec5f7d18298f51e8ae53db73/ab7ad7abb3660c58ffffdf07ff3bb976e7e0afa0

Timelineinfo

01/13/2026 CVE reserved
03/04/2026 +50 days Advisory disclosed
03/04/2026 +0 days VulDB entry created
06/24/2026 +112 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Researcher: the superblock
Status: Confirmed

CNA: Linux
CVE: CVE-2026-23238 (🔒)

GCVE (CVE): GCVE-0-2026-23238
GCVE (VulDB): GCVE-100-348732
EUVD: 🔒
CERT Bund: WID-SEC-2026-0614 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 03/04/2026 16:07
Updated: 06/24/2026 07:50
Changes: 03/04/2026 16:07 (59), 03/04/2026 18:02 (1), 03/05/2026 14:09 (7), 03/07/2026 22:18 (2), 03/18/2026 06:43 (11), 04/20/2026 11:35 (1), 04/29/2026 22:59 (1), 06/24/2026 07:50 (1)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

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