External risk intelligence

Linux Kernel SMC Use-After-Free Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-74493

This vulnerability exists within the Linux kernel's internal SMC (Shared Memory Communications) networking subsystem. It involves low-level socket management and race conditions during internal link group termination, which are not directly exposed to or reachable from the public internet in standard deployment patterns.

Use After Free

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 concerns a resolved issue within the Linux kernel's networking components, specifically related to the management of socket connections during link group termination. The vulnerability could potentially lead to system instability if exploited. The main concern is to confirm if this specific subsystem is in use and potentially exposed.

Unstable socket behavior during network termination.
Confirms usage of a specialized kernel networking feature.
Verify if this specific kernel function is actively used.

Attack Path

How an attacker could exploit the issue

An attacker could trigger a use-after-free vulnerability in the Linux kernel's networking component by exploiting a race condition between closing a socket and terminating a link group. This occurs when a connection's socket is freed prematurely during the termination process before a critical reference is taken. Successful exploitation could lead to system instability or potential code execution.

Requires local access.
Triggered by concurrent close and termination.
Risk of system crash or code execution.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could affect the behavior of the Linux kernel's networking subsystem when handling specific socket operations during link group termination. A race condition between closing a socket and terminating a link group might lead to unexpected system behavior.

Kernel networking socket integrity.
Concurrent close and termination overlap.
Unpredictable service behavior.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability impacts the Linux kernel's network subsystem, specifically related to socket management during link group termination. Infrastructure or platform teams responsible for the Linux kernel's network stack are likely to own this issue. The first practical step is to identify systems running the affected kernel version, confirm if the SMC functionality is actively used, and assess business criticality before planning remediation.

Infrastructure/Platform teams own resolution.
Verify SMC usage and affected systems.
Plan kernel updates during maintenance.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is the Linux SMC component affected by CVE-2026-74493?

SMC stands for Shared Memory Communications. It is a kernel networking subsystem designed to optimize data transfer between systems by allowing them to use shared memory instead of traditional network stack processing. It is primarily used in high-performance computing or specialized data center environments to reduce latency and CPU overhead for TCP-based applications.

What does use-after-free mean in this CVE?

This is a memory management flaw where the system attempts to access or use a socket connection after it has already been deleted or freed from memory. In this specific case, the kernel loses track of the connection's state during a cleanup process, creating a window where the system may mistakenly interact with invalid data, potentially leading to instability.

How is this race condition triggered?

The vulnerability requires a precise timing overlap between two events: an application closing a network socket and the system simultaneously terminating a link group. If these actions happen at the exact same time, the kernel might free the socket before it is finished processing the termination. Normal network activity or connections that are not undergoing termination do not trigger this issue.

Is my system at risk according to Halo Surface Signal?

Halo Surface Signal indicates this vulnerability is very unlikely to be reachable. Because the flaw exists deep within the kernel's internal SMC logic rather than at the network edge, it is not directly exposed to the public internet in standard configurations. The risk is constrained to systems where this specific, specialized networking feature is actively enabled and utilized.

What should I do if I run systems using this kernel feature?

First, verify if your environment actively utilizes the SMC networking subsystem, as it is often disabled by default. If it is in use, identify the specific kernel versions deployed across your infrastructure. Coordinate with your platform or infrastructure team to track official distribution patches and schedule a kernel update during your next standard maintenance window.

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.