CVE-2026-90138 Linux CVE debrief

Who should care

Linux kernel maintainers, administrators, and users of Linux-based systems should assess exposure and apply patches to prevent incorrect error responses in vsock_accept(). Affected operators, platform administrators, vulnerability management teams, and security teams should review and implement patches or mitigations to prevent incorrect error responses.

Why it matters

A vulnerability in the Linux kernel's vsock implementation can cause incorrect error responses when accepting incoming connections. Linux kernel maintainers, administrators, and users should assess exposure and apply patches.

• Verify Linux kernel versions to determine exposure.
• Apply patches to prevent incorrect error responses.
• Monitor incoming connections for incorrect error responses.

Technical summary

The Linux kernel's vsock implementation has a vulnerability that causes incorrect error responses when accepting incoming connections. The vsock_accept() function checks the listener's sk_err, which can hold an error from a previous self-connect attempt. This results in an incoming connection being rejected with an EPROTO error. A self-connect attempt can set sk_err to EPROTO due to the unexpected packet type. Linux kernel maintainers, administrators, and users of Linux-based systems should assess exposure and apply patches to prevent incorrect error responses in vsock_accept().

Defensive priority

Verify Linux kernel versions and apply patches to prevent incorrect error responses in vsock_accept().

Recommended defensive actions

• Verify Linux kernel versions and compare with known affected versions.
• Apply patches to update the vsock implementation.
• Monitor incoming connections for incorrect error responses.
• 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.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The CVE record and source item provide details on the vulnerability, including its description and affected versions. However, the corpus does not establish exploitation or specific impact, requiring verification from official sources.

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.