CVE-2026-64036 cgroup/rstat: validate cpu before css_rstat_cpu() access
A missing CPU validation in the Linux kernel's cgroup rstat BPF kfunc allows out-of-bounds access, potentially causing a system crash.
- 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-2026-64036?
CVE-2026-64036 is a high-severity memory corruption vulnerability in Linux kernel, published on 19 Jul 2026. 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:
cgroup/rstat: validate cpu before css_rstat_cpu() access
css_rstat_updated() is exposed as a BPF kfunc and accepts a caller-provided cpu argument. The function uses cpu for per-cpu rstat lookups without checking whether it refers to a valid possible CPU.
A BPF iter/cgroup program with CAP_BPF and CAP_PERFMON can pass an invalid cpu value. On an unfixed UBSCAN_BOUNDS test kernel, cpu == 0x7fffffff triggers:
UBSAN: array-index-out-of-bounds in kernel/cgroup/rstat.c:31:9 index 2147483647 is out of range for type 'long unsigned int [64]' Call Trace: css_rstat_updated bpf_iter_run_prog cgroup_iter_seq_show bpf_seq_read
Add cpu validation to the BPF-facing css_rstat_updated() kfunc and move the common implementation to __css_rstat_updated() for in-kernel callers.
Which versions are affected by CVE-2026-64036?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64036?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-64036 being exploited?
There is no known exploitation of CVE-2026-64036 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-92721, BELL-CVE-2026-64036, DEBIAN-CVE-2026-64036, GHSA-7cqc-fvgj-qm9h, ROOT-OS-DEBIAN-12-CVE-2026-64036, ROOT-OS-DEBIAN-13-CVE-2026-64036 and 1 more.