CVE-2026-103416 in ThreadX
Summary
by MITRE • 10/07/2026
Out-of-bounds write via the TLS 1.3 handshake message cache in NetX Duo in Eclipse ThreadX NetX Duo 6.5.1.202602 allows a handshake message larger than the cache writes past it and on into the rest of the session control block, which holds pointers. A malicious or compromised server can make a TLS 1.3 client produce such a message before certificate authentication completes, so no server certificate is needed to reach it.
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified in Eclipse ThreadX NetX Duo version 6.5.1.202602 represents a critical out-of-bounds write condition within the TLS 1.3 handshake message cache mechanism. This flaw stems from an insufficient validation of input data length during the processing of incoming network packets, specifically targeting the buffer allocated to store handshake messages. When a server transmits a TLS 1.3 handshake message that exceeds the predefined size limits of this internal cache, the application fails to perform proper bounds checking before copying the data into memory. Consequently, the write operation proceeds past the end of the designated buffer and overwrites adjacent memory regions within the session control block. This structural integrity failure allows an attacker to corrupt critical pointers and state variables that govern the ongoing TLS connection, potentially leading to arbitrary code execution or a denial of service condition depending on how the corrupted data is subsequently utilized by the network stack.
From a technical perspective, this vulnerability aligns with CWE-787: Out-of-bounds Write, as it involves writing data beyond the allocated boundaries of a buffer in memory. The specific attack vector leverages the TLS 1.3 protocol's handshake phase, where initial messages are exchanged before mutual authentication is fully established. Because the flaw can be triggered by sending an oversized message prior to certificate verification, it does not require the attacker to possess valid server credentials or certificates. This characteristic significantly lowers the barrier for exploitation, allowing any network-accessible adversary who can intercept or inject traffic into the communication channel to trigger the condition. The attack falls under MITRE ATT&CK technique T1078: Valid Accounts if used in conjunction with credential theft, but more accurately maps to T1496: Resource Hijacking via denial of service or potentially T1203: Exploitation for Client Execution if code execution is achieved through the corrupted pointers.
The operational impact of this vulnerability is severe due to its potential to compromise the confidentiality and integrity of encrypted communications. By corrupting the session control block, an attacker can manipulate how the TLS stack processes subsequent packets, potentially leading to a crash that disrupts service availability for embedded devices relying on NetX Duo for secure connectivity. In more sophisticated scenarios where memory layout permits it, the out-of-bounds write could allow an attacker to overwrite function pointers or return addresses within the session context, facilitating remote code execution with the privileges of the network stack process. This poses a significant risk in Internet of Things and industrial control systems where NetX Duo is commonly deployed, as these environments often lack robust memory protection mechanisms such as Address Space Layout Randomization or Data Execution Prevention at the application level.
Mitigation strategies must focus on immediate patching to version 6.5.1.202603 or later, which includes corrected bounds checking logic within the handshake message cache implementation. Until patches are applied, network administrators should implement strict ingress filtering rules that limit the maximum size of TLS handshake messages allowed through firewalls and intrusion detection systems. Additionally, deploying runtime application self-protection mechanisms or memory safety tools can help detect anomalous write operations to control blocks in real-time. It is also advisable to review deployment configurations for any exposed endpoints running vulnerable versions of NetX Duo and prioritize their remediation given the ease with which this vulnerability can be exploited without authentication credentials.