cgroup/rstat: validate cpu before css_rstat_cpu() access
CVE-2026-64036 · published 19 Jul 2026
How serious is it
- Severity: high, CVSS score 7.8 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-64036?
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Who is affected
- Linux Linux: a319185be9f5ad13c2a296d448ac52ffe45d194c to < b28b862b07257219755d0b0a7fbe5d23b7c9ea91, a319185be9f5ad13c2a296d448ac52ffe45d194c to < 3d595affbe00a2e8bf43b9f2947a8efcdc1c059e, a319185be9f5ad13c2a296d448ac52ffe45d194c to < 6a01413a4e8fcb0263d7bef5075c5f8f4eb3a8b6, a319185be9f5ad13c2a296d448ac52ffe45d194c to < fd2bd9fa7700ddf28296486b2598cff2f80cc819
- Linux Linux: 6.1
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
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.
Check your whole app
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References
- git.kernel.org/stable/c/b28b862b07257219755d0b0a7fbe5d23b7c9ea91
- git.kernel.org/stable/c/3d595affbe00a2e8bf43b9f2947a8efcdc1c059e
- git.kernel.org/stable/c/6a01413a4e8fcb0263d7bef5075c5f8f4eb3a8b6
- git.kernel.org/stable/c/fd2bd9fa7700ddf28296486b2598cff2f80cc819
- git.kernel.org/stable/c/8817005efbdfdf5d4e4814cb5dc52b53d12917d7
Merged from CVE List. Last updated 25 Oct 2026. All vulnerabilities · RSS · JSON