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/./" 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.

Classification

CVE ID: CVE-2025-21646

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 12.58% (scored less or equal to compared to others)

EPSS Date: 2025-02-17 (when was this score calculated)

References

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

Timeline