External risk intelligence

Linux Kernel Netfilter Flowtable Use-After-Free Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-74746

This vulnerability exists within the Linux kernel netfilter flowtable implementation. While it processes network traffic, it is a low-level kernel subsystem component. It is not a user-facing application or service, and direct exploitation requires specific local conditions or advanced network manipulation that is not characteristic of public-facing internet services.

Use After Free

Halo Surface Signal: 2 out of 5 — 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 network filtering component could allow unauthorized access and manipulation of data. The issue, which has been resolved, pertains to how network traffic flows are managed, and if exploited, could lead to system instability or data compromise. The main concern is confirming relevance and exposure.

Manages network traffic flows, impacting system stability.
Critical flaw could expose data and disrupt operations.
Confirm relevance and assess any potential exposure.

Attack Path

How an attacker could exploit the issue

An attacker could potentially reach this vulnerability by interacting with the Linux kernel's netfilter flowtable, a component responsible for managing network traffic flow. This interaction might involve sending specially crafted network packets or triggering specific kernel operations. If successful, this could lead to a use-after-free condition, allowing an attacker to read or write memory in an uncontrolled manner, potentially leading to system compromise.

No authentication or special privileges needed.
Triggered by operations on network flow tables.
Risk of memory corruption and system compromise.

Live Threat

Current exploitation, exposure, and threat context

When supported by the advisory, this vulnerability could allow an attacker to cause memory corruption within the Linux kernel's netfilter flowtable component, potentially impacting system stability and allowing for further system compromise.

Kernel memory corruption.
Triggered by network traffic processing.
System instability or compromise.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in the Linux kernel's netfilter flowtable component is likely the responsibility of the infrastructure or platform team managing the Linux systems. The first practical step is to identify all Linux systems running the affected kernel version, determine their exposure to external networks or internal untrusted zones, and identify the business criticality of any services relying on the netfilter functionality before planning remediation.

Infrastructure/Platform teams own the issue.
Verify Linux kernel exposure and criticality.
Plan risk-based remediation actions.

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 netfilter flowtable?

The netfilter flowtable is a core component within the Linux kernel that accelerates network traffic processing. It manages the state of active network connections, allowing the system to handle high volumes of data efficiently by offloading certain tasks. It sits deep within the operating system's networking stack, acting as the foundation that enables firewalls and traffic routing tools to function properly on Linux-based servers and devices.

What does this CVE-2026-74746 vulnerability mean?

This is a memory management flaw involving the improper sequencing of data entries. Because the kernel was publishing a flow before it was fully prepared, a background process could incorrectly access or free memory that was still in use. This leads to a use-after-free condition, where the system attempts to interact with memory addresses that are no longer valid, potentially causing instability or unauthorized memory access.

How is this vulnerability triggered?

It is triggered by the kernel's internal process of managing active network connections. Specifically, the race condition occurs during the insertion of new flow entries. It is not triggered by static configuration files or simple network connectivity alone; it requires specific, ongoing network traffic activity that hits the precise timing window where the flowtable is updating its internal records.

Is my system at risk?

Halo Surface Signal indicates that exploitation is unlikely for most systems. While the vulnerability exists in the networking stack, it is a low-level kernel component rather than a typical user-facing application. Because direct exploitation requires advanced network manipulation or specific local conditions, the risk is lower than for standard services exposed directly to the public internet.

What are the first steps to address this?

Your infrastructure team should begin by creating an inventory of all systems running the affected Linux kernel versions. Focus on identifying which of these servers perform high-volume network routing or firewall duties. Once identified, prioritize these systems for kernel updates provided by your distribution vendor, as these patches correct the internal flow sequencing logic to prevent the memory error.

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.