External risk intelligence

Linux Kernel CIFS Use-After-Free in Tree Connect.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2023-54280

This vulnerability exists within the Linux kernel CIFS (SMB) filesystem client implementation. It involves low-level tree connection handling and IPC management, which are internal kernel operations not directly exposed as public-facing services or network endpoints.

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 critical vulnerability in the Linux kernel's file-sharing component could allow attackers to disrupt system operations or access sensitive information. The issue stems from a race condition in how the system handles network connections for inter-process communication. While the direct impact is not immediately clear, it affects a fundamental part of the operating system.

A flaw exists in how the kernel handles file-sharing connections.
The concern is confirming relevance and exposure to business systems.
Leadership should monitor for confirmed exposure and related impacts.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by initiating a network connection to a vulnerable system. The attack targets the CIFS (SMB) client implementation within the Linux kernel, specifically during the process of establishing an IPC tree connection. Successfully triggering the vulnerability could lead to a use-after-free condition, potentially allowing an attacker to compromise the integrity and availability of the system.

Requires network access.
Triggers race condition during IPC tree connect.
Can lead to system compromise.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could affect the stability of systems using the Linux kernel's CIFS client when handling specific network operations. A use-after-free bug may occur during the process of establishing an IPC tree connection, potentially leading to crashes or other unpredictable behavior.

System stability and availability.
Race condition in tree connection handling.
Unpredictable service behavior or crashes.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in the Linux kernel's CIFS implementation requires attention from teams managing Linux infrastructure and potentially those responsible for network file sharing services. The immediate first step is to inventory all Linux systems utilizing CIFS, assess their exposure and business criticality, and identify the accountable system owners. Remediation planning should then be prioritized based on this risk assessment.

Linux infrastructure and platform teams.
Verify CIFS usage and reachability.
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 CIFS component?

The Common Internet File System (CIFS) client is a part of the Linux kernel that allows systems to mount and access shared files and printers over a network, typically using the SMB protocol. It enables Linux machines to interact with Windows-based file shares or other network-attached storage devices, serving as a fundamental driver for networked data exchange.

How does CVE-2023-54280 cause a use-after-free error?

This vulnerability involves a race condition where the kernel attempts to access hostname information while simultaneously freeing it in another thread. Because the memory is released before the process is finished using it, the system ends up referencing invalid or repurposed data. This memory corruption can lead to unpredictable system behavior or stability issues.

Do I need to be connected to a specific network to trigger this?

Yes, an attacker must be able to initiate a network connection that interacts with the CIFS client's IPC tree connection process. Simply having a Linux system is not enough; the bug is specifically triggered during the internal handling of these network file-sharing requests. Standard, local, non-networked file operations do not trigger this flaw.

Is my system at risk according to Halo Surface Signal?

Halo Surface Signal identifies this as very unlikely to be directly reachable. The vulnerability exists deep within kernel-level CIFS client operations rather than in public-facing network services. Because these IPC management tasks are internal, they are not typically exposed as direct endpoints that an external attacker can influence over the internet.

When should I prioritize fixing this vulnerability?

You should prioritize this by first identifying all Linux servers in your environment that actively use CIFS to mount remote network shares. Once you have a list of these systems, assess their criticality to your operations. Use this inventory to plan updates or patching for the affected infrastructure, focusing on systems where CIFS connectivity is essential for business continuity.

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.