CVE-2026-93221 Linux CVE debrief

Who should care

Linux kernel developers and maintainers, Linux distribution vendors, and users of Linux-based systems that utilize the nfsd subsystem, as well as security teams and vulnerability management teams responsible for assessing and mitigating the impact of this vulnerability on their systems.

Why it matters

This vulnerability affects the Linux kernel's nfsd subsystem and can lead to data corruption and potential denial-of-service (DoS) attacks. Linux kernel developers and maintainers, Linux distribution vendors, and users of Linux-based systems that utilize the nfsd subsystem should assess their exposure and apply the provided patches to mitigate the vulnerability.

• Data corruption and double-free vulnerability
• Potential for denial-of-service (DoS) attacks
• Elevation of privileges may be possible

Technical summary

The vulnerability is caused by the lack of proper synchronization when accessing boolean fields in the nfsd_net structure. This issue can be exploited by multiple concurrent threads, leading to a double-free vulnerability and data corruption. The fix involves replacing the scattered boolean fields with a single unsigned long flags word and an enum nfsd_net_flag for the bit positions. This change ensures that the access to these fields is properly synchronized, preventing the double-free vulnerability and data corruption. Linux kernel developers and maintainers should assess their exposure and apply the provided patches to mitigate the vulnerability.

Defensive priority

High

Recommended defensive actions

• Review and apply the provided kernel patches to address the vulnerability
• Ensure that the Linux kernel is updated to a version that includes the fix
• Monitor system logs for potential exploitation attempts
• Perform vulnerability scanning to identify potentially affected systems
• Implement 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 vulnerability is caused by the lack of proper synchronization when accessing boolean fields in the nfsd_net structure. This issue can be exploited by multiple concurrent threads, leading to a double-free vulnerability and data corruption.

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.