CVE-2025-68299 afs: Fix delayed allocation of a cell's anonymous key
A null pointer dereference in the Linux kernel AFS filesystem can cause a system crash when mounting a cell before the anonymous key is allocated.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-68299?
CVE-2025-68299 is a vulnerability in Linux, published on 16 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
afs: Fix delayed allocation of a cell's anonymous key
The allocation of a cell's anonymous key is done in a background thread along with other cell setup such as doing a DNS upcall. In the reported bug, this is triggered by afs_parse_source() parsing the device name given to mount() and calling afs_lookup_cell() with the name of the cell.
The normal key lookup then tries to use the key description on the anonymous authentication key as the reference for request_key() - but it may not yet be set and so an oops can happen.
This has been made more likely to happen by the fix for dynamic lookup failure.
Fix this by firstly allocating a reference name and attaching it to the afs_cell record when the record is created. It can share the memory allocation with the cell name (unfortunately it can't just overlap the cell name by prepending it with "afs@" as the cell name already has a '.' prepended for other purposes). This reference name is then passed to request_key().
Secondly, the anon key is now allocated on demand at the point a key is requested in afs_request_key() if it is not already allocated. A mutex is used to prevent multiple allocation for a cell.
Thirdly, make afs_request_key_rcu() return NULL if the anonymous key isn't yet allocated (if we need it) and then the caller can return -ECHILD to drop out of RCU-mode and afs_request_key() can be called.
Note that the anonymous key is kind of necessary to make the key lookup cache work as that doesn't currently cache a negative lookup, but it's probably worth some investigation to see if NULL can be used instead.
Which versions are affected by CVE-2025-68299?
How do I fix CVE-2025-68299?
Apply the vendor's patch.
Is CVE-2025-68299 being exploited?
There is no known exploitation of CVE-2025-68299 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2025-68299, GHSA-wq3w-wxhr-h474, UBUNTU-CVE-2025-68299.