External risk intelligence

Linux Kernel TCP Socket Operation Flag Race Condition

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-74268

This vulnerability exists deep within the Linux kernel's TCP stack handling of socket state transitions during connection establishment failure. It is an internal memory and lock management issue not directly reachable or exploitable as a network service or application-layer interface.

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory addresses a vulnerability in the Linux kernel's handling of network connections. Specifically, it involves how the system manages temporary socket operations when a new connection is being set up but then fails. The issue could lead to unexpected behavior or system instability if exploited.

Kernel issue with failed network connections.
Matters for system stability and integrity.
Confirm relevance and exposure.

Attack Path

How an attacker could exploit the issue

An attacker could trigger a flaw in the Linux kernel's TCP connection handling, specifically when a child socket inherits certain flags from a listener. If the setup of this child socket fails, it can lead to an internal kernel warning and a denial of service when the system attempts to close the socket. This occurs because the kernel expects a lock to be held during a specific state transition, but it is released prematurely.

Vulnerability in TCP stack's socket handling.
Triggered by failed child socket setup.
Leads to kernel warning and denial of service.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could impact the internal state management of network sockets within the Linux kernel. Under specific failure conditions during the handling of new TCP connections, the kernel may encounter an inconsistent state, potentially affecting the proper functioning of socket operations. No system or user data is directly exposed or modified, and there is no indication of risk to PII.

Internal socket state management.
Failed connection setup paths.
Potential for service instability.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability resides in the Linux kernel's TCP connection handling, specifically related to socket operations and BPF callbacks during the initial connection setup. Infrastructure or platform teams managing Linux systems are most likely to be responsible for addressing this. The first practical step is to identify all Linux systems that could be affected, assess their exposure, and then plan remediation, potentially coordinating with kernel developers or downstream distributors for timely updates.

Infrastructure/Platform teams own resolution.
Verify affected Linux systems and exposure.
Plan and deploy kernel updates.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is the Linux kernel's TCP stack?

It is the fundamental component of the Linux operating system that manages network traffic using the Transmission Control Protocol (TCP). It handles creating connections, reliable data transfer, and socket management. In this context, it manages child sockets created when a listener socket receives a new connection attempt.

How does this CVE-2026-74268 vulnerability work?

This is a memory and locking synchronization issue. When a new TCP connection fails to initialize, the kernel attempts to close the child socket. Due to a flaw, the kernel tries to trigger BPF callbacks while the necessary socket lock is not held. This inconsistency results in a kernel warning and potential system instability.

When does this vulnerability trigger?

The flaw triggers specifically during the cleanup process of a failed child socket connection attempt. It does not occur during successful, established connections. If a connection is never established, the kernel should not invoke these specific callback functions, which is where the race condition occurs.

How relevant is this to my infrastructure?

According to Halo Surface Signal, this vulnerability is very unlikely to be exploited. It resides deep within internal kernel memory management and is not directly reachable through standard network services or application-layer interfaces. It is primarily an internal stability concern.

What is the first step to address this?

Infrastructure and platform teams should review their Linux system inventories to identify kernels that require updates. Since this involves a core component of the operating system, you should look for official patches or kernel updates released by your Linux distribution provider to resolve the underlying socket state handling flaw.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.