HighFix available

afs: Fix the maximum cell name length

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: afs: Fix the maximum cell name length The kafs filesystem limits the maximum length of a cell to 256 bytes, but a problem occurs if someone actually does that: kafs tries to create a directory under /proc/net/afs/ with the name of the cell, but that fails with a warning: WARNING: CPU: 0 PID: 9 at fs/proc/generic.c:405 because procfs limits the maximum filename length to 255. However, the DNS limits the maximum lookup length and, by extension, the maximum cell name, to 255 less two (length count and trailing NUL). Fix this by limiting the maximum acceptable cellname length to 253. This also allows us to be sure we can create the "/afs/./" mountpoint too. Further, split the YFS VL record cell name maximum to be the 256 allowed by the protocol and ignore the record retrieved by YFSVL.GetCellName if it exceeds 253.

Products: Kernel
Affected versions: Not specified
Fixed versions: 5.10.234, 5.15.177, 6.1.125, 6.12.10, 6.6.72
CVEs: CVE-2025-21646
Confirmed fixed CVEs: Not specified
Updated in this feed: 3 Nov 2026, 15:43 UTC · Revision 1

Source evidence

afs: Fix the maximum cell name length

core-osv · Original source

Published 19 Jan 2025, 10:18 UTC

osv:CVE-2025-21646

Kernel

Fixed versions: 5.10.234, 5.15.177, 6.1.125, 6.6.72, 6.12.10

Complete source record

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  "url": "https://osv.dev/vulnerability/CVE-2025-21646",
  "method": "structured",
  "payload": {
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    "title": "afs: Fix the maximum cell name length",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: afs: Fix the maximum cell name length The kafs filesystem limits the maximum length of a cell to 256 bytes, but a problem occurs if someone actually does that: kafs tries to create a directory under /proc/net/afs/ with the name of the cell, but that fails with a warning: WARNING: CPU: 0 PID: 9 at fs/proc/generic.c:405 because procfs limits the maximum filename length to 255. However, the DNS limits the maximum lookup length and, by extension, the maximum cell name, to 255 less two (length count and trailing NUL). Fix this by limiting the maximum acceptable cellname length to 253. This also allows us to be sure we can create the \"/afs/./\" mountpoint too. Further, split the YFS VL record cell name maximum to be the 256 allowed by the protocol and ignore the record retrieved by YFSVL.GetCellName if it exceeds 253.",
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      "modified": "2026-10-28T02:30:30.137059944Z",
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      "references": [
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  "source_id": "core-osv",
  "document_id": 496941,
  "published_at": "2025-01-19T10:18:02.776+00:00"
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