CVE-2025-21646: afs: Fix the maximum cell name length
First published: Sun Jan 19 2025(Updated: )
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/.<cell>/" 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.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Red Hat Kernel-devel | ||
| debian/linux | <=5.10.223-1 | 5.10.234-1 6.1.129-1 6.1.128-1 6.12.20-1 6.12.21-1 |
| debian/linux-6.1 | 6.1.129-1~deb11u1 |
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Reference Links
- https://git.kernel.org/stable/c/9340385468d056bb700b8f28df236b81fc86a079
- https://git.kernel.org/stable/c/7cb3e77e9b4e6ffa325a5559393d3283c9af3d01
- https://git.kernel.org/stable/c/aabe47cf5ac5e1db2ae0635f189d836f67024904
- https://git.kernel.org/stable/c/7673030efe0f8ca1056d3849d61784c6caa052af
- https://git.kernel.org/stable/c/7922b1f058fe24a93730511dd0ae2e1630920096
- https://git.kernel.org/stable/c/8fd56ad6e7c90ac2bddb0741c6b248c8c5d56ac8
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-21646
- https://nvd.nist.gov/vuln/detail/CVE-2025-21646
- https://launchpad.net/bugs/cve/CVE-2025-21646
- https://security-tracker.debian.org/tracker/CVE-2025-21646
- https://ubuntu.com/security/CVE-2025-21646
- https://git.kernel.org/linus/8fd56ad6e7c90ac2bddb0741c6b248c8c5d56ac8
Frequently Asked Questions
What is the severity of CVE-2025-21646?
The severity of CVE-2025-21646 is classified as moderate due to potential denial-of-service impacts.
How do I fix CVE-2025-21646?
To fix CVE-2025-21646, you should update to the latest version of the Linux kernel where the vulnerability has been patched.
What systems are affected by CVE-2025-21646?
CVE-2025-21646 affects all versions of the Linux kernel that utilize the kafs filesystem.
What are the potential impacts of CVE-2025-21646?
The potential impacts of CVE-2025-21646 include system instability and denial of service when exceeding the maximum cell name length.
When was CVE-2025-21646 reported?
CVE-2025-21646 was reported in early 2025, highlighting an issue with the kafs filesystem in the Linux kernel.
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