Vulnerability Database

374,566

Total vulnerabilities in the database

CVE-2026-23238 — linux / linux_kernel

Reachable Assertion

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.

  • Published: Mar 4, 2026
  • Updated: Mar 18, 2026
  • CVE: CVE-2026-23238
  • Severity: Medium
  • Exploit:
  • CISA KEV:

CVSS v3:

  • Severity: Medium
  • Score: 5.5
  • AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CWEs:

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

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Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

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