External risk intelligence

Linux Kernel xfrm skb Double-Free Vulnerability.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-92489

This vulnerability exists within the internal Linux kernel networking stack specifically regarding XFRM (IPsec) packet handling. It is a low-level memory management issue occurring during internal kernel processing paths and is not directly exposed as a service or reachable interface to the public internet.

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 critical vulnerability has been addressed in the Linux kernel, specifically within its network packet handling for XFRM. This issue could allow for unintended memory operations, potentially impacting system stability and security. The main concern is to confirm if this specific kernel function is utilized within your environment.

Memory handling error in Linux kernel.
Potential system instability or security impact.
Confirm relevance and exposure within your systems.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted network packets. This would cause the Linux kernel's XFRM subsystem to incorrectly free memory that is still in use, leading to a crash and potential denial of service.

No special access required.
Triggered by network packet.
Risks system stability.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could affect the internal processing of network packets within the Linux kernel, specifically related to XFRM (IPsec) functionality. When a specific packet handling path is taken and netfilter drops the packet, a double-free memory condition may occur. This condition could lead to system instability or unexpected behavior.

Kernel packet processing data.
Double-free memory condition.
System instability or crashes.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability resides within the Linux kernel's XFRM (IPsec) packet handling. Ownership will likely fall to the infrastructure or platform teams managing Linux systems, with potential coordination needed from network or security teams if XFRM is actively used. The first step is to confirm if XFRM is enabled and processing traffic on critical systems, then identify the accountable system owner to plan remediation.

Infrastructure or platform team ownership.
Verify XFRM usage and network reachability.
Plan remediation based on system criticality.

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 XFRM subsystem?

XFRM is the framework within the Linux kernel that manages IPsec, a suite of protocols used to secure network communications by encrypting and authenticating IP packets. It acts as the underlying engine that handles data transformation, such as encrypting traffic between servers or establishing virtual private networks, ensuring that network operations remain private and intact.

How does a double-free vulnerability work in CVE-2026-92489?

A double-free happens when a program attempts to release the same memory space twice. In this case, the kernel's network code incorrectly frees a data structure (the skb) that it no longer technically owns. Because the system still tracks that memory as active, attempting to clear it again causes a logic error that can lead to system crashes or unstable behavior.

When does this vulnerability trigger during network processing?

The flaw triggers specifically when the XFRM subsystem attempts to send a packet directly and encounters a scenario where the internal netfilter component drops that packet. It does not trigger during standard, successful packet delivery. The issue arises solely from a mismanaged hand-off of memory ownership when a packet is rejected mid-process.

Do I need to worry if my system is not internet-facing?

According to Halo Surface Signal, this vulnerability is very unlikely to be exploited from the internet because it exists deep within internal kernel networking functions rather than at a public-facing service interface. While it is a critical-severity memory management issue, the specific path required to trigger it makes it less accessible to external attackers compared to typical web-service flaws.

Is my system impacted by this Linux kernel issue?

Impact depends on whether your systems actively utilize XFRM/IPsec for network traffic. Your first step should be to confirm if XFRM is configured and handling traffic on your Linux infrastructure. Once you verify usage, coordinate with your platform or infrastructure teams to review kernel updates, as the resolution requires patching the underlying kernel code.

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.