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VulnerabilityPublished Updated

CVE-2025-21646: Linux kernel · afs: Fix the maximum cell name length

Affects Linux kernelSource GCVE Database

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Not known to be exploited · CVSS 7.5 High · fixed in 5.15.0-1080.87~20.04.1 : patch Linux kernel soon.

Data as of 29 Oct 2026, 22:37 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 5.15.0-1080.87~20.04.1, 5.15.0-1086.95~20.04.1, 5.15.0-1081.90~20.04.1 +62
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 19 Jan 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: 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 29 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
  • <6.8.0-60.63
Fixed in
  • 6.8.0-60.63
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threatsAffected
  • <6.8.0-1029.31
Fixed in
  • 6.8.0-1029.31
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threatsAffected
  • <6.8.0-1029.34
Fixed in
  • 6.8.0-1029.34
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther threatsAffected
  • <6.11.0-1012.12~24.04.1
Fixed in
  • 6.11.0-1012.12~24.04.1
Ubuntu 24.04 LTSlinux-azure-nvidiapkg:deb/ubuntu/linux-azure-nvidia?arch=source&distro=nobleOther threatsAffected
  • <6.8.0-1016.17
Fixed in
  • 6.8.0-1016.17
Ubuntu 24.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=nobleOther threatsAffected
  • <6.8.0-1030.32
Fixed in
  • 6.8.0-1030.32

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

AI-suggested

A patch is available and has been released in Linux kernel versions 5.15.0-1074.77~20.04.1 and later. Users and administrators should upgrade affected Linux kernel versions to these fixed releases to resolve the issue. No additional mitigation actions are required beyond applying the official kernel updates.

Description

CVE-2025-21646 addresses a vulnerability in the Linux kernel's AFS filesystem related to the maximum allowed cell name length. The kafs filesystem allowed cell names up to 256 bytes, but procfs limits filenames to 255 bytes, causing warnings and potential failures when creating directories under /proc/net/afs/. The fix limits the maximum cell name length to 253 bytes to ensure compatibility with procfs and DNS lookup limits. This also ensures mountpoints under /afs/.<cell>/ can be created reliably. The YFS VL record cell name maximum remains 256 bytes as per protocol, but names exceeding 253 bytes are ignored. This vulnerability has been fixed in multiple Linux kernel versions starting with 5.15.0-1074.77~20.04.1 and later.

References

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