VulnerabilityPublished 19 Jul 2026

CVE-2026-64036: Linux kernel · cgroup/rstat: validate cpu before css_rstat_cpu() access

Source GCVE Database

Authoritative record:CVE-2026-64036· High 7.8

Not known to be exploited · CVSS 7.8 High · fixed in fd2bd9fa7700ddf28296486b2598cff2f80cc819 : patch Linux kernel soon.

Data as of 26 Oct 2026, 12:55 UTC

CVSS 3.1 base score

7.8High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in fd2bd9fa7700ddf28296486b2598cff2f80cc819, b28b862b07257219755d0b0a7fbe5d23b7c9ea91, 8817005efbdfdf5d4e4814cb5dc52b53d12917d7 +2

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-7cqc-fvgj-qm9h

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ a319185be9f5ad13c2a296d448ac52ffe45d194c, < fd2bd9fa7700ddf28296486b2598cff2f80cc819	Fixed in fd2bd9fa7700ddf28296486b2598cff2f80cc819
LinuxLinux	Affected ≥ a319185be9f5ad13c2a296d448ac52ffe45d194c, < b28b862b07257219755d0b0a7fbe5d23b7c9ea91	Fixed in b28b862b07257219755d0b0a7fbe5d23b7c9ea91
LinuxLinux	Affected ≥ a319185be9f5ad13c2a296d448ac52ffe45d194c, < 8817005efbdfdf5d4e4814cb5dc52b53d12917d7	Fixed in 8817005efbdfdf5d4e4814cb5dc52b53d12917d7
LinuxLinux	Affected ≥ a319185be9f5ad13c2a296d448ac52ffe45d194c, < 6a01413a4e8fcb0263d7bef5075c5f8f4eb3a8b6	Fixed in 6a01413a4e8fcb0263d7bef5075c5f8f4eb3a8b6
LinuxLinux	Affected ≥ a319185be9f5ad13c2a296d448ac52ffe45d194c, < 3d595affbe00a2e8bf43b9f2947a8efcdc1c059e	Fixed in 3d595affbe00a2e8bf43b9f2947a8efcdc1c059e
LinuxLinux	Affected =6.1	Fixed in–

AI-suggested

A fix has been implemented in the Linux kernel to validate CPU arguments in css_rstat_updated(). Users and administrators should apply the official kernel updates that include this patch once available. Until then, restricting access to CAP_BPF and CAP_PERFMON capabilities can reduce risk.

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.

Impact

Exploitation of this vulnerability could cause a kernel memory safety error (array index out-of-bounds), potentially leading to kernel crashes or undefined behavior. However, exploitation requires elevated capabilities (CAP_BPF and CAP_PERFMON), limiting the attack surface to privileged or semi-privileged users. There are no known exploits in the wild.

Summary

The Linux kernel vulnerability CVE-2026-64036 involves the css_rstat_updated() BPF kfunc in the cgroup/rstat subsystem, which accepted a CPU argument without validating whether it referred to a valid possible CPU. This lack of validation allowed a privileged BPF iter/cgroup program (with CAP_BPF and CAP_PERFMON) to pass an invalid CPU value, leading to an out-of-bounds array access detected by UBSAN in kernel/cgroup/rstat.c. The issue was fixed by adding CPU validation in css_rstat_updated() and moving the core logic to __css_rstat_updated() for safer in-kernel calls.

References

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