CyberSecBulletin
CVE-2026-64036NVD status: Modified

Linux: Improper Validation of Array Index

Published Updated By the CyberSecBulletin desk

CVE-2026-64036 is a high-severity improper validation of array index vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions ee5afb74688aa6f1f16d8c7e7b6bfaf803fb62fc, b28b862b07257219755d0b0a7fbe5d23b7c9ea91, 3d595affbe00a2e8bf43b9f2947a8efcdc1c059e as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.13% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to ee5afb74688aa6f1f16d8c7e7b6bfaf803fb62fc or b28b862b07257219755d0b0a7fbe5d23b7c9ea91 or 3d595affbe00a2e8bf43b9f2947a8efcdc1c059e or 6a01413a4e8fcb0263d7bef5075c5f8f4eb3a8b6, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.18.34 or 7.0.11, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxa319185be9f5ad13c2a296d448ac52ffe45d194c up to, but not including, ee5afb74688aa6f1f16d8c7e7b6bfaf803fb62fc; a319185be9f5ad13c2a296d448ac52ffe45d194c up to, but not including, b28b862b07257219755d0b0a7fbe5d23b7c9ea91; a319185be9f5ad13c2a296d448ac52ffe45d194c up to, but not including, 3d595affbe00a2e8bf43b9f2947a8efcdc1c059e; a319185be9f5ad13c2a296d448ac52ffe45d194c up to, but not including, 6a01413a4e8fcb0263d7bef5075c5f8f4eb3a8b6; a319185be9f5ad13c2a296d448ac52ffe45d194c up to, but not including, fd2bd9fa7700ddf28296486b2598cff2f80cc819; a319185be9f5ad13c2a296d448ac52ffe45d194c up to, but not including, 8817005efbdfdf5d4e4814cb5dc52b53d12917d7; 6.1ee5afb74688aa6f1f16d8c7e7b6bfaf803fb62fc, b28b862b07257219755d0b0a7fbe5d23b7c9ea91, 3d595affbe00a2e8bf43b9f2947a8efcdc1c059e, 6a01413a4e8fcb0263d7bef5075c5f8f4eb3a8b6, fd2bd9fa7700ddf28296486b2598cff2f80cc819, 8817005efbdfdf5d4e4814cb5dc52b53d12917d7
LinuxLinux Kernel6.1 up to, but not including, 6.18.34; 6.19 up to, but not including, 7.0.11; 7.16.18.34, 7.0.11

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Validation of Array Index

The product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array.

How developers prevent this class of flaw

  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, Ada allows the programmer to constrain the values of a variable and languages such as Java and Ruby will allow the programmer to handle exceptions when an out-of-bounds index is accessed.
  • Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment. For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND.

More Improper Validation of Array Index vulnerabilities (CWE-129)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Improper Validation of Array Index vulnerabilities

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