CVE-2024-26736

What it actually does

Insufficient stack buffer size in afs_update_volume_status allows overflow when formatting a volume vid value that can reach 20 characters plus NUL terminator.

Why it matters to the business

Unpatched Linux kernels supporting AFS volumes risk memory corruption that can cause system instability or crashes during normal volume status operations.

How an attack unfolds

An attacker supplies or triggers an AFS volume whose vid string is crafted to exceed the original idbuf capacity, causing adjacent stack memory to be overwritten when the string is written without length checking.

How to fix it

Apply the upstream fix that enlarges idbuf to 24 bytes and switches to snprintf; the change is present in commit 5c27d85a69fa16a08813ba37ddfb4bbc9a1ed6b5 and all subsequent stable kernels that include it.

How to confirm the fix worked

Inspect the afs_update_volume_status function in the running kernel source or verify the kernel build contains the referenced commit; confirm idbuf declaration is at least 24 bytes and snprintf is used.

Typical attack path

1. Identify or create an AFS volume whose vid field is at least 21 characters
2. Cause the kernel to invoke afs_update_volume_status on that volume
3. Trigger the unchecked string formatting into the undersized idbuf
4. Achieve stack overwrite leading to crash or potential control-flow hijack

How to detect it

Review kernel logs for stack buffer overflow or oops messages referencing afs_update_volume_status; examine audit or syscall logs for unusual AFS volume status operations around any crash timestamps.

What your security team should do

• Upgrade affected kernels to a version containing commit 5c27d85a69fa16a08813ba37ddfb4bbc9a1ed6b5 or later
• Prioritize systems that mount or manage AFS volumes
• Monitor for kernel oops or stack corruption reports involving afs_update_volume_status