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Out-of-Bounds Write via Unsanitized Prefix Length in Router Advertisement Processing in FreeRTOS-Plus-TCP

High
AniruddhaKanhere published GHSA-97qg-4359-xm3x Apr 29, 2026

Package

No package listed

Affected versions

>=V4.0.0 AND <=V4.2.5, >=V4.3.0 AND <=V4.4.0

Patched versions

V4.2.6, V4.4.1

Description

Summary

FreeRTOS-Plus-TCP is an open source TCP/IP stack implementation specifically designed for FreeRTOS. The stack provides a standard Berkeley sockets interface and supports essential networking protocols including IPv6, ARP, DHCP, DNS, LLMNR, mDNS, NBNS, RA, ND, ICMP, and ICMPv6.

A bounds-write issue exists in FreeRTOS-Plus-TCP's IPV6 Router Advertisement (RA) packet processing, where an incorrect length value can cause the system to write beyond the allocated memory buffer.

Impact

In the FreeRTOS-Plus-TCP IPV6 Router Advertisement processing which may allow an unauthenticated adjacent-network actor to compromise devices via rogue RA packet.

A section of Router Advertisement processing lacks sufficient validation of length fields during packet parsing, allowing their use in memory operations without proper bounds checking. This can lead to out-of-bounds memory writes. The issue can be exploited by any device on the local network that can send crafted Router Advertisement packets.

New version V4.2.6 and V4.4.1 adds additional input validation to the RA option parser to reject malformed values before they reach sensitive operations.

Any device using FreeRTOS-Plus-TCP versions between V4.0.0 through V4.2.5 and V4.3.0 through V4.4.0, processing Router Advertisement packets is affected by this risk. Update to version V4.4.1 and V4.2.6 or later to fix this.

Patches

This issue has been addressed in FreeRTOS-Plus-TCP version V4.4.1 and V4.2.6. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.

Workarounds

  • Implement network-level filtering to block untrusted Router Advertisement packets on the local network segment.
  • Deploy devices on isolated network segments where rogue RA packets cannot be injected.

References

If you have any questions or comments about this advisory, we ask that you contact AWS Security via our issue reporting page or directly via email to aws-security@amazon.com. Please do not create a public GitHub issue.

Acknowledgement

We would like to thank @Eun0us from Espilon for collaborating on this issue through the coordinated issue disclosure process.

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Adjacent
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

CVE ID

CVE-2026-7426

Weaknesses

No CWEs

Credits