CVE-2026-52957 libceph: Fix potential null-ptr-deref in decode_choose_args()
A null pointer dereference in the Linux kernel's Ceph client allows a remote attacker to cause a denial of service via a crafted OSD map message.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-52957?
CVE-2026-52957 is a high-severity vulnerability in Linux kernel, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
libceph: Fix potential null-ptr-deref in decode_choose_args()
A message of type CEPH_MSG_OSD_MAP contains an OSD map that itself contains a CRUSH map. When decoding this CRUSH map in crush_decode(), an array of max_buckets CRUSH buckets is decoded, where some indices may not refer to actual buckets and are therefore set to NULL. The received CRUSH map may optionally contain choose_args that get decoded in decode_choose_args(). When decoding a crush_choose_arg_map, a series of choose_args for different buckets is decoded, with the bucket_index being read from the incoming message. It is only checked that the bucket index does not exceed max_buckets, but not that it doesn't point to an index with a NULL bucket. If a (potentially corrupted) message contains a crush_choose_arg_map including such a bucket_index, a null pointer dereference may occur in the subsequent processing when attempting to access the bucket with the given index.
This patch fixes the issue by extending the affected check. Now, it is only attempted to access the bucket if it is not NULL.
Weakness: CWE-476
Which versions are affected by CVE-2026-52957?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-52957?
Apply the vendor's patch.
Is CVE-2026-52957 being exploited?
There is no known exploitation of CVE-2026-52957 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-90321, BELL-CVE-2026-52957, DEBIAN-CVE-2026-52957, GHSA-7qv9-42rg-qh56, ROOT-OS-DEBIAN-11-CVE-2026-52957, ROOT-OS-DEBIAN-12-CVE-2026-52957 and 3 more.