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CVE-2026-55392 nilfs-dev CVE debrief

The NILFS utilities through version 2.3.0 contain a vulnerability where the nilfs_sb_is_valid() function fails to properly validate the s_log_block_size field in the NILFS2 superblock. This oversight allows attackers to supply crafted NILFS2 images that can trigger undefined behavior, resulting in either oversized shifts or out-of-memory conditions. Such exploitation can crash tools like nilfs-tune and dumpseg. This issue was fixed in commit 26efb5d. Users of NILFS utilities should update to the latest version to mitigate this vulnerability.

Vendor
nilfs-dev
Product
nilfs-utils
CVSS
MEDIUM 6.7
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-18
Original CVE updated
2026-06-18
Advisory published
2026-06-18
Advisory updated
2026-06-18

Who should care

Users and administrators utilizing NILFS utilities, particularly those handling NILFS2 images, should be aware of this vulnerability. Developers and maintainers of NILFS utilities are also advised to review and apply the necessary patches.

Technical summary

The nilfs_sb_is_valid() function in NILFS utilities through 2.3.0 does not validate the s_log_block_size field in the NILFS2 superblock before performing bit-shift operations. This omission enables attackers to provide crafted NILFS2 images that can cause undefined behavior, leading to crashes in tools such as nilfs-tune and dumpseg. The issue was addressed with a validation fix in commit 26efb5d.

Defensive priority

Medium

Recommended defensive actions

  • Update NILFS utilities to the latest version that includes the fix from commit 26efb5d.
  • Validate the integrity of NILFS2 images before processing.
  • Implement additional checks on the s_log_block_size field in the NILFS2 superblock.
  • Use secure channels for obtaining and distributing NILFS2 images.
  • Monitor for and apply future updates to NILFS utilities.
  • Consider using alternative file systems or tools with more robust validation mechanisms.

Evidence notes

The information provided is based on the CVE-2026-55392 record and references from the NVD and GitHub. The vulnerability was publicly disclosed and addressed via a commit in the NILFS utilities repository.

Official resources

CVE-2026-55392 was published on 2026-06-18T19:16:23.630Z and modified on 2026-06-18T20:16:15.263Z.