CVE-2026-89671 Linux CVE debrief

Who should care

Linux administrators and users who rely on nfsd for file sharing and access control should be aware of this vulnerability and take necessary actions to prevent potential ACL drops. They should review system configurations to ensure proper ACL settings and prevent unauthorized access. Additionally, they should monitor system logs for potential exploitation attempts to detect potential attacks. Security teams and vulnerability management teams should also be

Why it matters

A vulnerability in the Linux kernel's nfsd could allow an attacker to drop a file's access control list (ACL) or default ACL, potentially impacting access control.

• Verify Linux kernel versions and apply patches if necessary to prevent potential ACL drops
• Review system configurations to ensure proper ACL settings and prevent unauthorized access
• Monitor system logs for potential exploitation attempts to detect potential attacks

Technical summary

The Linux kernel's nfsd has a vulnerability where it does not properly gate nfs3 setacl by argp->mask, potentially allowing an attacker to drop a file's ACL or default ACL. This vulnerability can be resolved by applying patches that implement the proper gating of nfs3 setacl by argp->mask, thus preventing the silent drops of ACLs. The vulnerability affects Linux kernel versions and can be mitigated by updating to the latest version or applying the provided patches. The vulnerability has been resolved through specific commits that gate nfs3 setacl by argp->mask, preventing silent drops of ACLs.

Defensive priority

Verify Linux kernel versions and apply patches if necessary.

Recommended defensive actions

• Verify Linux kernel versions and apply patches if necessary
• Review system configurations and ensure proper ACL settings
• Monitor system logs for potential exploitation attempts
• 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.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.

Evidence notes

The CVE record and source item provide details on the vulnerability, including its description and affected versions. The Linux kernel's nfsd has a vulnerability where it does not properly gate nfs3 setacl by argp->mask, potentially allowing an attacker to drop a file's ACL or default ACL. The source item and CVE record provide evidence of the vulnerability's existence and its potential impact on access control.

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.