External risk intelligence

Linux Kernel rxrpc Double-Release Use-After-Free

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-74434

This vulnerability is located within the Linux kernel's rxrpc implementation, which handles low-level network protocol processing. It is not a service or application directly exposed to the internet; exploitation requires local access or interaction with specific kernel-level functions, making it unlikely to be reachable as a public-facing service.

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 vulnerability in the Linux kernel's networking component could lead to memory corruption and system instability. It arises from how certain network messages are handled when being read without being fully consumed. While the direct exposure is limited, confirming if this specific kernel function is in use is important.

A kernel bug affects network message handling.
It could cause system instability if triggered.
Confirm if this kernel component is in use.

Attack Path

How an attacker could exploit the issue

An attacker could exploit a flaw in the Linux kernel's rxrpc message handling to cause memory corruption. This occurs when a specific network message is peeked at, causing it to be incorrectly managed in memory queues. If an attacker can trigger this condition, it may lead to a crash or further system compromise.

Entry condition: No privileges needed.
Trigger point: Reading a special network message.
Resulting risk: Memory corruption and crashes.

Live Threat

Current exploitation, exposure, and threat context

When processing out-of-band messages with `MSG_PEEK`, the Linux kernel's rxrpc subsystem could encounter memory corruption and use-after-free vulnerabilities due to incorrect message handling. This can occur when a message is simultaneously present on two internal queues, leading to data integrity issues.

Kernel memory state.
Network message processing.
System instability or crashes.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in the Linux kernel's rxrpc module requires investigation by infrastructure and platform teams. The first practical step is to identify all Linux systems running the affected kernel, confirm their reachability and criticality, and then assign ownership for remediation.

Identify and confirm affected systems.
Determine business criticality and exposure.
Plan remediation with kernel owners.

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's rxrpc component?

The rxrpc component is a subsystem within the Linux kernel that handles the implementation of the RX remote procedure call protocol. It is primarily used to facilitate network communications for services that rely on this specific protocol. Because it operates at the kernel level, it manages low-level data structures and queues to ensure network messages are processed and routed correctly between the network interface and internal system memory.

What does the vulnerability in CVE-2026-74434 actually mean?

This is a memory management flaw involving how the kernel handles network messages when they are 'peeked' at without being removed from a queue. The system incorrectly places the same message into two different memory queues simultaneously. This causes internal data pointers to overwrite each other, leading to a condition where the kernel attempts to free the same memory multiple times, resulting in a use-after-free error and potential system memory corruption.

How is this Linux kernel vulnerability triggered?

An attacker must prompt the kernel to process an out-of-band network message using the MSG_PEEK flag. The flaw occurs when this peek operation incorrectly moves the message into a pending queue while it still resides in the original reception queue. Notably, standard operations that consume the message normally do not trigger this specific double-queue conflict; the issue is highly specific to the way the kernel incorrectly manages peeked data structures.

Is my system reachable over the internet according to Halo Surface Signal?

Halo Surface Signal indicates that this vulnerability is very unlikely to be reachable as a public-facing service. While the kernel processes network traffic, the specific rxrpc functions involved are deep-seated components that typically do not serve as direct entry points from the internet. This suggests that the risk of remote, unauthenticated exploitation is low, as the vulnerability requires specialized interaction with low-level kernel protocol processing.

What should I do first to address CVE-2026-74434?

The immediate priority is to identify which of your systems are running a version of the Linux kernel that includes the rxrpc module. Since this is a kernel-level issue, remediation involves identifying, inventorying, and patching the affected infrastructure. Work with your platform or system administration teams to verify if your specific kernel configuration utilizes this module and schedule updates according to your organization's standard lifecycle maintenance processes.

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.