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VulnerabilityPublished Updated

CVE-2025-21721: Linux kernel · nilfs2: handle errors that nilfs_prepare_chunk() may return

Affects Linux kernelSource GCVE Database

0

Not known to be exploited · CVSS 5.5 Medium · fixed in 5.4.0-1146.156~18.04.1 : update Linux kernel when convenient.

Data as of 28 Oct 2026, 11:14 UTC

CVSS 3.1 base score
5.5Medium
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 5.4.0-1146.156~18.04.1, 5.4.0-1151.158~18.04.1, 5.4.0-1149.158~18.04.1 +84
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 27 Feb 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threatsAffected
  • <6.8.0-64.67
Fixed in
  • 6.8.0-64.67
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threatsAffected
  • <6.8.0-1032.34
Fixed in
  • 6.8.0-1032.34
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threatsAffected
  • <6.8.0-1034.39
Fixed in
  • 6.8.0-1034.39
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther threatsAffected
  • <6.11.0-1015.15~24.04.1
Fixed in
  • 6.11.0-1015.15~24.04.1
Ubuntu 24.04 LTSlinux-azure-nvidiapkg:deb/ubuntu/linux-azure-nvidia?arch=source&distro=nobleOther threatsAffected
  • <6.8.0-1022.23
Fixed in
  • 6.8.0-1022.23
Ubuntu 24.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=nobleOther threatsAffected
  • <6.8.0-1033.35
Fixed in
  • 6.8.0-1033.35

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

In the Linux kernel, the following vulnerability has been resolved: nilfs2: handle errors that nilfs_prepare_chunk() may return Patch series "nilfs2: fix issues with rename operations". This series fixes BUG_ON check failures reported by syzbot around rename operations, and a minor behavioral issue where the mtime of a child directory changes when it is renamed instead of moved. This patch (of 2): The directory manipulation routines nilfs_set_link() and nilfs_delete_entry() rewrite the directory entry in the folio/page previously read by nilfs_find_entry(), so error handling is omitted on the assumption that nilfs_prepare_chunk(), which prepares the buffer for rewriting, will always succeed for these. And if an error is returned, it triggers the legacy BUG_ON() checks in each routine. This assumption is wrong, as proven by syzbot: the buffer layer called by nilfs_prepare_chunk() may call nilfs_get_block() if necessary, which may fail due to metadata corruption or other reasons. This has been there all along, but improved sanity checks and error handling may have made it more reproducible in fuzzing tests. Fix this issue by adding missing error paths in nilfs_set_link(), nilfs_delete_entry(), and their caller nilfs_rename().

References

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