CVE-2025-21646

/// Technical description

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.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References