External risk intelligence

Linux Kernel NFS Use-After-Free Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-74730

This vulnerability exists within the Linux kernel's NFS client implementation. NFS is typically deployed within internal, trusted network segments for file sharing and is not designed to be exposed directly to the public internet.

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 recent security advisory addresses a vulnerability in the Linux kernel's Network File System (NFS) component. This issue could potentially allow for unauthorized access or manipulation of data if exploited, impacting systems that utilize NFS for file sharing. The primary concern is to confirm if our environment is affected by this specific kernel vulnerability.

A kernel flaw could impact NFS data handling.
Understand the risk to connected systems.
Confirm relevance and verify exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted network requests to a system running a vulnerable Linux kernel. If a network file system (NFS) operation is in progress and a state ID is freed prematurely, it could lead to a use-after-free condition. This could result in a system crash, unauthorized data access, or modification of sensitive information.

Entry condition: Network access to NFS services.
Trigger point: Delayed FREE_STATEID operation.
Resulting risk: System instability and data compromise.

Live Threat

Current exploitation, exposure, and threat context

A use-after-free vulnerability in the Linux kernel's NFS client could allow an attacker to crash the system or potentially gain elevated privileges when a `FREE_STATEID` operation is delayed. This could impact the integrity and availability of the NFS service.

NFS server state data at risk.
Exploited when `FREE_STATEID` operation is delayed.
System instability or unauthorized access.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in the Linux kernel's NFS implementation requires attention from teams managing Linux infrastructure and NFS services. The first practical step is to identify all systems running the affected kernel version, determine their exposure, and confirm ownership before planning remediation within maintenance windows.

Linux infrastructure and NFS teams own.
Verify NFS service exposure and criticality.
Plan kernel updates during maintenance.

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 NFS component?

The Network File System (NFS) is a core Linux kernel technology that allows systems to access files over a network as if they were stored locally. It is widely used in data centers and enterprise environments to share directories and manage distributed storage across multiple servers. Because it operates at the kernel level to handle high-speed data transfers, any flaw here impacts how the operating system manages memory for network operations.

How does CVE-2026-74730 cause a use-after-free error?

This vulnerability involves a memory management mistake during NFS communications. When the system performs a FREE_STATEID operation, it must track the associated data structures. If a delay occurs, the kernel might prematurely delete the memory related to the server state while the operation is still trying to use it. This creates a use-after-free condition, where the system attempts to access memory that has already been deallocated or repurposed.

Do I need to worry about any network request triggering this?

Not every network interaction triggers this flaw. The vulnerability specifically requires a scenario where a FREE_STATEID operation is delayed or interrupted during an NFS transaction. Normal, successful file system operations that complete without these specific delays do not encounter the broken state handling that leads to this use-after-free error.

Is my NFS service at risk if it is behind a firewall?

According to Halo Surface Signal, NFS is generally deployed within internal, trusted network segments rather than being exposed directly to the public internet. While the CVSS severity is high, the practical risk often depends on whether your infrastructure permits untrusted network traffic to communicate directly with your NFS service ports.

When should I plan to address this kernel vulnerability?

The first step is to perform an inventory of all systems running the affected Linux kernel versions. Once you have identified these assets, verify which servers are actively utilizing NFS services. Prioritize patching these systems according to your standard maintenance windows, focusing on environments where the NFS implementation could be reachable by unauthorized parties.

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.