Essential FreeRTOS-Plus-TCP Flaw Permits Code Execution or System Crash

A vital reminiscence corruption vulnerability, tracked as CVE-2025-5688, has been disclosed in FreeRTOS-Plus-TCP, Amazon’s open-source TCP/IP stack extensively utilized in embedded and IoT units.

The flaw, rated 8.4 (Excessive) on the CVSS scale, is rooted in how the stack processes Hyperlink-Native Multicast Title Decision (LLMNR) and Multicast DNS (mDNS) queries containing excessively lengthy DNS names, particularly when Buffer Allocation Scheme 1 is enabled.

FreeRTOS-Plus-TCP is engineered for FreeRTOS environments, supporting a broad array of networking protocols—IPv6, ARP, DHCP, DNS, LLMNR, mDNS, NBNS, RA, ND, ICMP, and ICMPv6—through an ordinary Berkeley sockets interface.

To handle community buffers, the stack gives two allocation schemes:

• Scheme 1: Allocates from a fixed-size buffer pool.
• Scheme 2: Dynamically allocates buffers from the heap as wanted.

The vulnerability manifests solely underneath Scheme 1, the place buffers are of fastened measurement.

When LLMNR or mDNS is enabled, and a question with a DNS identify longer than the buffer’s capability is acquired, the code fails to adequately test the size, resulting in an out-of-bounds write.

This may end up in system crashes or, in a worst-case situation, arbitrary code execution on the goal system.

Weak Variations and Influence

The difficulty impacts the next FreeRTOS-Plus-TCP variations:

• LLMNR: v2.3.4 by v4.3.1 with Buffer Allocation Scheme.
• mDNS: v4.0.0 by v4.3.1 with Buffer Allocation Scheme.

The vulnerability is extreme as a result of it requires no person interplay, no privileges, and has a low assault complexity.

Exploitation may compromise the confidentiality, integrity, and availability of embedded techniques, making them a high-value goal for attackers in industrial, medical, and client IoT deployments.

Patch Particulars and Code-Degree Mitigation

The AWS safety workforce, in collaboration with Purdue College, addressed the flaw in model 4.3.2 of FreeRTOS-Plus-TCP.

The patch introduces strict bounds checking to stop buffer overflows throughout LLMNR and mDNS question dealing with.

Whereas the precise patched code just isn’t totally disclosed, the core repair includes validating the size of incoming DNS names earlier than copying them into fixed-size buffers.

A typical defensive sample may resemble:

cif (name_length > MAX_DNS_NAME_LENGTH) {
    // Reject the packet or truncate safely
    return ERROR_INVALID_NAME;
}
memcpy(buffer, incoming_name, name_length);

This ensures that any DNS identify exceeding the buffer’s capability is dealt with gracefully, stopping reminiscence corruption.

No Workarounds Out there

There are not any viable workarounds for this vulnerability.

Techniques should improve to FreeRTOS-Plus-TCP v4.3.2 or later.

Builders sustaining customized forks or by-product codebases ought to combine the upstream patch instantly.

Broader Safety Implications

Given FreeRTOS’s widespread adoption in vital embedded environments, this vulnerability underscores the significance of rigorous enter validation in community protocol implementations.

Reminiscence corruption in low-level community stacks generally is a gateway to distant code execution, persistent malware, or denial-of-service assaults, particularly in resource-constrained IoT units the place safety controls could also be restricted.

Amazon and the FreeRTOS neighborhood urge all customers to replace promptly and monitor for by-product vulnerabilities in associated protocol handlers.

The coordinated disclosure course of, together with contributions from Purdue College, highlights the worth of academic-industry collaboration in securing foundational open-source infrastructure.

For additional technical particulars and the most recent patched releases, seek the advice of the official [FreeRTOS-Plus-TCP GitHub repository.

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