External risk intelligence

Linux Kernel Double Free Vulnerability in rtase Module

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-74545

This vulnerability is located deep within the Linux kernel network driver code related to DMA mapping and fragment handling. It is not a network-facing service, API, or application, and requires specific internal kernel-level execution paths, making it unavailable to remote public internet traffic.

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 vulnerability in the Linux kernel has been resolved, addressing a flaw in how network data fragments are handled during data transmission. This issue could potentially lead to unintended system behavior if certain error conditions are met. The primary concern is to confirm if our systems utilize the affected components and are exposed.

Kernel flaw involves data transmission errors.
Understanding exposure is leadership's key role.
Confirm relevance and determine potential impact.

Attack Path

How an attacker could exploit the issue

An attacker could potentially exploit this vulnerability by triggering a specific error condition within the Linux kernel's network transmission handling. This occurs when mapping data fragments for direct memory access (DMA) fails after some fragments have already been successfully mapped. The flawed error handling then attempts to free the same memory buffer twice, which can lead to memory corruption and potentially impact the system's integrity and availability.

Network access required for initial exposure.
Triggered by a DMA mapping failure.
High risk to system integrity and availability.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability in the Linux kernel's rtase driver could allow for a double-free error when handling multi-fragment network packets under specific DMA mapping failure conditions. This internal error condition might affect the stability of network packet processing.

Kernel network packet processing.
DMA mapping failures in specific code paths.
System instability or crashes.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in the Linux kernel's network transmission code, specifically within the `rtase` driver, requires immediate attention from teams managing Linux systems. The primary action is to identify all instances of the affected kernel version and assess their exposure. Infrastructure or platform teams are likely responsible for kernel updates, but confirmation of ownership and the business criticality of affected systems is the crucial first step before planning remediation.

Kernel developers and infrastructure teams own resolution.
Verify affected Linux systems and their reachability.
Plan kernel updates during scheduled 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 rtase module in the Linux kernel?

The rtase module is a network driver used within the Linux kernel to manage data transmission for specific network interface hardware. It handles the complex task of preparing data packets for delivery, which includes managing memory buffers and Direct Memory Access (DMA) operations to ensure efficient communication between the network card and system memory.

What does a double-free vulnerability mean in CVE-2026-74545?

A double-free is a memory management error that occurs when a program attempts to release the same computer memory location twice. In this specific case, if a transmission error occurs, the kernel erroneously tries to free the memory buffer for a network packet after it has already been freed, which can cause system crashes or memory corruption.

How is this double-free flaw triggered?

The bug is triggered only when a specific error occurs during network transmission: a DMA mapping failure must happen after some, but not all, data fragments have been processed. If the system is operating normally and successfully maps all data fragments, the flawed code path that causes the double-free is not executed.

Is my system at risk from external network attacks?

According to Halo Surface Signal, this vulnerability is very unlikely to be exploited from the internet. The issue resides deep within low-level kernel driver code rather than an exposed network service or application, meaning it cannot be directly triggered by remote public traffic.

What steps should I take to address this vulnerability?

Start by identifying systems running the affected Linux kernel version. Since this requires a kernel-level update, coordinate with your infrastructure or platform teams to plan the necessary patches during your next scheduled maintenance window to ensure system stability.

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.