External risk intelligence

Linux Kernel SMB Client Use-After-Free Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2023-54076

The vulnerability exists within the Linux kernel CIFS/SMB client implementation. This is a local kernel-level component used by systems to mount network shares. It is not an internet-facing service or application, and it does not listen for or accept public network connections.

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

A recently resolved vulnerability in the Linux kernel's handling of network file sharing could allow for unauthorized access to or modification of data, and disruption of services. While the issue has been fixed, its potential impact highlights the importance of maintaining kernel integrity for secure data operations.

Kernel flaw could impact data access and services.
Important to verify if your systems use this kernel feature.
Confirm relevance and exposure for affected systems.

Attack Path

How an attacker could exploit the issue

An attacker could potentially exploit this vulnerability by leveraging the Linux kernel's SMB client component. If an attacker can trick the system into interacting with a malicious SMB server or manipulate existing SMB sessions, they might be able to trigger a use-after-free condition. This could allow them to gain elevated privileges or crash the system.

No special access needed.
Triggered by SMB session operations.
Allows arbitrary code execution.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability in the Linux kernel's SMB client could allow an unauthenticated attacker to cause a system crash or potentially execute code. This may occur when the system attempts to manage network share connections, leading to an unstable or compromised system state.

System stability and integrity.
Mismanaged network share connections.
Potential for system instability or compromise.

Operational Fix

Recommended remediation, mitigation, and detection steps

The Linux kernel's SMB client implementation is likely managed by the infrastructure or platform team responsible for the operating system. The initial step is to identify all systems running the affected kernel, assess their exposure and business criticality, and then engage the system owners to plan remediation during the next maintenance window.

Identify impacted systems and owners.
Verify SMB client reachability and criticality.
Plan remediation based on risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the Linux kernel SMB client?

The Linux kernel SMB client is a core operating system component that enables a computer to connect to and mount remote network file shares, such as those hosted on Windows servers or NAS devices. It allows Linux systems to interact with remote files as if they were stored locally on the machine's own filesystem.

What does CVE-2023-54076 mean in simple terms?

This vulnerability is a use-after-free weakness. It occurs when the kernel mismanages how it tracks connections to network shares. If the system incorrectly releases a connection reference while it is still being used, it creates an unstable state that an attacker could potentially manipulate to crash the system or force it to execute unauthorized code.

How is this vulnerability triggered?

The flaw is triggered during specific SMB session operations where the system fails to correctly count or protect active connections. It does not occur through standard, well-behaved file access; rather, it requires interactions that confuse the kernel's reference tracking, such as connecting to a malicious or specifically crafted network share.

Is my system at risk according to Halo Surface Signal?

Halo Surface Signal indicates that risk is very unlikely because this vulnerability resides in a local kernel component, not an internet-facing service. The SMB client acts as a network consumer, meaning it does not listen for incoming public connections, which significantly limits how an attacker could interact with it.

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

First, verify your inventory to identify systems running the affected Linux kernel version. Once identified, consult your system administrators or platform team to confirm if the SMB client feature is actively used. If it is, prioritize the inclusion of the official kernel patch in your upcoming system maintenance and update schedule.

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.