CVE-2026-7426

High

Published: 29 April 2026

Published

29 April 2026

Modified

04 May 2026

KEV Added

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Patch

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CVSS Score 8.1 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

EPSS Score 0.0002 5.4th percentile

Risk Priority 16 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-7426 is a high-severity Out-of-bounds Write (CWE-787) vulnerability in Amazon Freertos-Plus-Tcp. Its CVSS base score is 8.1 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation of Remote Services (T1210); ranked at the 5.4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploitation of Remote Services (T1210). What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

SI-10 requires validation of information inputs like the IPv6 RA prefix length field to prevent heap buffer overflows from malformed packets.

SI-2 Flaw Remediation good match

prevent

SI-2 mandates timely flaw remediation by upgrading to FreeRTOS-Plus-TCP versions V4.2.6 or V4.4.1 that fix the validation flaw.

SI-16 Memory Protection partial match

prevent

SI-16 implements memory protection mechanisms that mitigate the impact of heap buffer overflows triggered by invalid prefix lengths.

MITRE ATT&CK Enterprise TechniquesAI

T1210 Exploitation of Remote Services Lateral Movement

Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.

attack.mitre.org →

Why these techniques?

Heap buffer overflow in IPv6 RA processing allows adjacent network attacker to exploit remote network stack software for memory corruption and high integrity/availability impact.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

Insufficient validation of the prefix length field in IPv6 Router Advertisement processing in FreeRTOS-Plus-TCP before V4.2.6 and V4.4.1 allows an adjacent network actor to cause memory corruption by sending a crafted Router Advertisement with a prefix length value exceeding the…

maximum valid length, resulting in a heap buffer overflow. Users processing IPv4 RA only are not impacted. To mitigate this issue, users should upgrade to the fixed version when available.

Deeper analysisAI

CVE-2026-7426 is a heap buffer overflow vulnerability stemming from insufficient validation of the prefix length field during IPv6 Router Advertisement (RA) processing in FreeRTOS-Plus-TCP versions before V4.2.6 and V4.4.1. An attacker can trigger the issue by sending a crafted IPv6 RA with a prefix length exceeding the maximum valid value, leading to memory corruption. Systems configured to process only IPv4 RAs are unaffected. The vulnerability is rated with a CVSS v3.1 base score of 8.1 (AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H) and maps to CWE-787 (Out-of-bounds Write).

An adjacent network attacker with low complexity and no privileges required can exploit this vulnerability by transmitting a malicious IPv6 RA packet to a vulnerable device. Successful exploitation results in high-impact integrity and availability disruptions through heap memory corruption, though confidentiality is not affected. The attack requires adjacency on the local network (AV:A), making it feasible in scenarios like shared wireless networks or misconfigured LAN segments where the target processes IPv6 RAs.

Advisories recommend upgrading to FreeRTOS-Plus-TCP V4.2.6 or V4.4.1, which address the validation flaw. Relevant resources include the AWS security bulletin at https://aws.amazon.com/security/security-bulletins/2026-023-aws/, GitHub release tags for the fixed versions at https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/releases/tag/V4.2.6 and https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/releases/tag/V4.4.1, and the GitHub security advisory at https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/security/advisories/GHSA-97qg-4359-xm3x.