CVE-2026-89564 Linux CVE debrief

Who should care

Linux kernel developers and maintainers, network administrators, and security teams responsible for ensuring the security and integrity of Linux-based systems. They should assess exposure and verify kernel patches to ensure the vulnerability is resolved. Additionally, operators and platform teams should review system configurations and network settings to identify potential vulnerabilities and implement compensating controls as needed.

Why it matters

The Linux kernel vulnerability could potentially cause issues with IPv4 and IPv6 input, multicast packet forwarding, and sock_pfree() invocation. Linux kernel developers, maintainers, network administrators, and security teams should assess exposure and verify kernel patches to ensure the vulnerability is resolved.

• Potential issues with IPv4 and IPv6 input when preserving an skb->sk association.
• Possible multicast packet forwarding issues after the receive-side RCU section ends.
• Need to verify and apply kernel patches to ensure the vulnerability is resolved.
• Potential for sock_pfree() to invoke and dereference the stale skb->sk.

Technical summary

The Linux kernel vulnerability could potentially cause issues with IPv4 and IPv6 input when preserving an skb->sk association. This association is used for local delivery under RCU. The issue arises when a multicast packet is not locally deliverable and is handed to ip6_mr_input() or ip_mr_input(), which can put the skb on an unresolved multicast route queue or forward it after the receive-side RCU section ends.

Defensive priority

Medium

Recommended defensive actions

• Review and apply the kernel patch to ensure the vulnerability is resolved.
• Monitor network traffic for potential exploitation attempts.
• Verify that the Linux kernel is up-to-date with the latest security patches.
• Perform a thorough review of system configurations and network settings to identify potential vulnerabilities.
• Implement compensating controls, such as firewalls or intrusion detection systems, to mitigate potential risks.
• Conduct regular security audits and vulnerability assessments to identify and address potential weaknesses.
• Track and analyze system logs to detect potential exploitation attempts.

Evidence notes

The CVE record and NVD vulnerability detail page provide information on the vulnerability. However, the evidence is limited, and further verification is required to determine the full scope of the vulnerability.

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.