CVE-2026-90291 Linux CVE debrief

Who should care

Linux kernel maintainers, Linux distribution maintainers, and users of Linux kernel versions that have not been patched may be vulnerable to use-after-free attacks. These individuals should assess exposure and verify if their systems are using affected kernel versions. Those using Linux kernel versions that have not been patched may be vulnerable to use-after-free attacks.

Why it matters

A use-after-free vulnerability was found in the Linux kernel's kmod dups code. The vulnerability can be used to gain elevated privileges or crash the system. Defenders should assess exposure and verify if their systems are using affected kernel versions. Those using Linux kernel versions that have not been patched may be vulnerable to use-after-free attacks. Remediation priority is high for Linux kernel maintainers and users.

• Defenders should assess exposure and verify if their systems are using affected kernel versions.
• Those using Linux kernel versions that have not been patched may be vulnerable to use-after-free attacks.
• The vulnerability can be used to gain elevated privileges or crash the system.
• Remediation priority is high for Linux kernel maintainers and users.

Technical summary

The kmod dups code in the Linux kernel uses RCU to ensure that a kmod_dup_req instance is freed only after it is no longer referenced. However, parallel users referencing the instance in kmod_dup_request_exists_wait don't enter an RCU read-side critical section, which can result in a use-after-free. The issue is fixed by changing the lifecycle management of kmod_dup_req to use reference counting. This change ensures that the kmod_dup_req instance is not freed prematurely, preventing the use-after-free vulnerability.

Defensive priority

Linux kernel maintainers and users should assess exposure and verify if their systems are using affected kernel versions. Those using Linux kernel versions that have not been patched may be vulnerable to use-after-free attacks.

Recommended defensive actions

• Assess exposure by checking if the Linux kernel version in use is affected.
• Verify if the patch for the kmod dups code has been applied.
• Consider updating to a patched Linux kernel version.
• Monitor systems for potential use-after-free attacks.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The CVE record and NVD entry provide details about the vulnerability, including its description, CVSS score, and affected systems. The kmod dups code in the Linux kernel uses RCU to ensure that a kmod_dup_req instance is freed only after it is no longer referenced. However, parallel users referencing the instance in kmod_dup_request_exists_wait don't enter an RCU read-side critical section, which can result in a use-after-free. The issue is fixed by changing the lifecycle management of kmod_dup_req to use reference counting. Evidence,

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.