CVE-2026-64036 Details
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.
A vulnerability exists in the Linux kernel's cgroup subsystem, specifically within the rstat component. The issue arises because the 'css_rstat_updated()' function, which is exposed as a BPF (Berkeley Packet Filter) kfunc, accepts a caller-provided CPU argument without validating its legitimacy. This oversight allows a BPF iter/cgroup program, granted with CAP_BPF and CAP_PERFMON, to pass an invalid CPU value. On an unpatched kernel with the UBSCAN_BOUNDS test, an invalid CPU value triggers an out-of-bounds array access, as indicated by the Undefined Behavior Sanitizer (UBSAN) error. The vulnerability has been addressed by adding CPU validation to the BPF-facing 'css_rstat_updated()' kfunc and moving the common implementation to '__css_rstat_updated()' for in-kernel callers.
Users can upgrade to the latest version of the Linux kernel where this vulnerability has been fixed. Instructions for downloading the patched kernel can be found on the official Linux kernel website.
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CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
No SSVC data is available for this CVE.
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Weakness Enumeration
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Affected Products
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 20, 2026 | CVE Modified | kernel.org |
| Jul 19, 2026 | New CVE Received | kernel.org |