CVE-2023-53421 blk-cgroup: Reinit blkg_iostat_set after clearing in blkcg_reset_stats()
A missing re-initialization in the Linux kernel block cgroup code can cause a NULL pointer dereference, leading to a kernel panic and denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-53421?
CVE-2023-53421 is a medium-severity vulnerability in Linux kernel, published on 18 Sep 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:
blk-cgroup: Reinit blkg_iostat_set after clearing in blkcg_reset_stats()
When blkg_alloc() is called to allocate a blkcg_gq structure with the associated blkg_iostat_set's, there are 2 fields within blkg_iostat_set that requires proper initialization - blkg & sync. The former field was introduced by commit 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") while the later one was introduced by commit f73316482977 ("blk-cgroup: reimplement basic IO stats using cgroup rstat").
Unfortunately those fields in the blkg_iostat_set's are not properly re-initialized when they are cleared in v1's blkcg_reset_stats(). This can lead to a kernel panic due to NULL pointer access of the blkg pointer. The missing initialization of sync is less problematic and can be a problem in a debug kernel due to missing lockdep initialization.
Fix these problems by re-initializing them after memory clearing.
Weakness: CWE-476
Which versions are affected by CVE-2023-53421?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2023-53421?
Apply the vendor's patch.
Is CVE-2023-53421 being exploited?
There is no known exploitation of CVE-2023-53421 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-71915, BELL-CVE-2023-53421, DEBIAN-CVE-2023-53421, GHSA-63xc-pmjj-q4vj, ROOT-OS-DEBIAN-11-CVE-2023-53421, ROOT-OS-DEBIAN-12-CVE-2023-53421 and 2 more.