AWS Advises on FreeRTOS-Plus-TCP DHCPv6 Integer Underflow Vulnerability

Amazon Web Services (AWS) has published a security bulletin addressing CVE-2026-7424, a vulnerability in the FreeRTOS-Plus-TCP networking stack. The advisory identifies an integer underflow issue within the DHCPv6 sub-option parser component of the software library.

The vulnerability, tracked as CVE-2026-7424, stems from how the FreeRTOS-Plus-TCP stack processes DHCPv6 sub-options. According to the AWS Security Bulletins, the specific flaw is an integer underflow in the parser responsible for handling these network configuration details. This type of error can occur when arithmetic operations on integer variables result in values that fall below the minimum representable value, potentially leading to unexpected behavior or memory corruption during packet processing.

Technical Context and Background

FreeRTOS-Plus-TCP is a widely used TCP/IP stack designed for embedded systems running the FreeRTOS real-time operating system. It provides the necessary networking capabilities for IoT devices and other resource-constrained hardware to connect to networks and the internet. The DHCPv6 protocol is the IPv6 counterpart to DHCP, used for automatically assigning IP addresses and other configuration information to devices on a network.

The integer underflow in the sub-option parser suggests that malformed or specifically crafted DHCPv6 packets containing certain sub-option data could trigger the vulnerability. In embedded networking stacks, parsers are critical components that must handle incoming network traffic robustly. Failures in these parsers, such as integer underflows, can compromise the stability and security of the device, potentially allowing for denial-of-service conditions or, in some cases, more severe exploitation depending on the system's architecture and security controls.

Who Is Affected

The advisory directly impacts users and developers who have integrated the FreeRTOS-Plus-TCP stack into their embedded software projects. This includes manufacturers of IoT devices, industrial control systems, and other embedded hardware that rely on FreeRTOS for their operating system and FreeRTOS-Plus-TCP for network connectivity. Any device using this specific version of the stack that processes DHCPv6 traffic is potentially vulnerable to the integer underflow issue.

Organizations deploying IoT fleets should review their bill of materials and software versions to determine if they are using the affected FreeRTOS-Plus-TCP implementation. The scope of the impact depends on whether the devices are exposed to untrusted networks where an attacker could send malicious DHCPv6 packets.

What should you do?

AWS has published this advisory to inform the community of the vulnerability. At this time, the source material does not confirm the availability of a patch, fix, or updated version of the FreeRTOS-Plus-TCP stack that resolves CVE-2026-7424. Users should monitor official channels from AWS and the FreeRTOS project for updates regarding remediation.

What to do and how to stay safe: AWS

• Verify if your embedded devices or IoT products use the FreeRTOS-Plus-TCP stack and check the specific version against affected releases once details are confirmed by the vendor.
• Restrict network access for vulnerable devices by ensuring they only communicate with trusted DHCPv6 servers in controlled environments, reducing exposure to malicious packets.
• Implement network segmentation to isolate IoT devices from critical infrastructure and general corporate networks, limiting the potential impact of a compromised device.
• Monitor official security advisories from AWS and the FreeRTOS project for the release of a patch or updated library version that addresses the integer underflow.

Step-by-step guide: Risk Based Vulnerability Management: Prioritize Fixes by Actual Threat

General security guidance from the Threat Times newsroom. It is not confirmed advice from the organisations named in this story.

Frequently asked questions

What is CVE-2026-7424?

CVE-2026-7424 is an integer underflow vulnerability in the DHCPv6 sub-option parser within the FreeRTOS-Plus-TCP networking stack, as detailed in an AWS Security Bulletin.

Which software is affected by this vulnerability?

The FreeRTOS-Plus-TCP stack, which is used in embedded systems running the FreeRTOS operating system, is affected by this vulnerability.

Has a fix been released for CVE-2026-7424?

The source material does not confirm that a patch or fix has been released; it only notes the publication of the security advisory by AWS.