CVE-2026-90647 in ASE2000 Communication Test Set
Summary
by MITRE • 09/13/2026
ASE/Kalkitech ASE2000 V2 Communication Test Set 2.35 through 2.37 on Windows contains an improper certificate validation vulnerability in the IEC 60870-5-104 TLS client (Task Mode). This allows a network-positioned attacker to bypass certificate validation via a certificate with multiple simultaneous faults, enabling a Man-in-the-Middle attack on protected communications.
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Analysis
by VulDB Data Team • 09/13/2026
The ASE/Kalkitech ASE2000 V2 Communication Test Set versions 2.35 through 2.37 contain a critical security flaw within its implementation of the IEC 60870-5-104 protocol stack, specifically affecting the Transport Layer Security (TLS) client functionality operating in Task Mode. This vulnerability stems from an improper validation mechanism for X.509 certificates during the TLS handshake process. In secure industrial communications, certificate validation is paramount to ensure that a device is communicating with its intended counterpart and not an impersonator. The flaw allows an attacker who possesses network access to present a maliciously crafted certificate that contains multiple simultaneous faults or inconsistencies. Instead of rejecting this invalid certificate as required by standard security protocols, the vulnerable software fails to detect these anomalies, thereby accepting it as valid. This failure in validation logic effectively neutralizes one of the primary defenses against identity spoofing in encrypted communications.
The operational impact of this vulnerability is severe, as it enables a Man-in-the-Middle (MitM) attack scenario where an adversary can intercept, read, and potentially modify sensitive data transmitted between devices using the IEC 60870-5-104 protocol. This protocol is widely used in power utility automation systems for telemetry and remote control operations. By bypassing certificate validation, an attacker positioned on the network segment can establish a trusted encrypted session with both ends of the communication without either party realizing they are communicating with an intermediary rather than each other. This compromises the confidentiality and integrity of critical infrastructure data, potentially allowing unauthorized commands to be issued or operational parameters to be altered undetected. Such actions could lead to significant disruptions in power distribution, false telemetry readings, or even physical damage to equipment if control signals are manipulated.
From a classification perspective, this vulnerability aligns with CWE-295 Improper Certificate Validation and CWE-347 Improper Verification of Cryptographic Signature, as the core issue lies in the failure to rigorously check certificate attributes and signatures against established trust anchors. In terms of adversary tactics, this flaw facilitates techniques associated with MITM attacks under the ATT&CK framework, specifically T1557 Adversary-in-the-Middle, which describes how attackers position themselves between two communicating parties to eavesdrop or alter communications. The ability to bypass validation via certificates with multiple faults suggests a lack of robust error handling and strict adherence to RFC 5280 standards for certificate processing, making the system susceptible to sophisticated phishing-style attacks within industrial control systems where network segmentation may be less rigorous than in general enterprise environments.
Mitigation strategies must focus on immediate patching and enhanced configuration controls. The primary remediation is to apply the vendor-provided software update that addresses this specific validation logic error in versions 2.35 through 2.37 of the ASE2000 V2 Communication Test Set. Until patches are applied, network administrators should implement strict access control lists (ACLs) and firewall rules to restrict TLS connections on port 2404 exclusively to known, trusted IP addresses, thereby limiting the attack surface for network-positioned adversaries. Additionally, enabling mutual authentication where both client and server must present valid certificates can provide an additional layer of security, although this requires careful management of certificate authorities within the industrial environment. Regular vulnerability scanning focused on TLS configuration weaknesses and monitoring for anomalous traffic patterns indicative of MitM attempts are also recommended to detect potential exploitation activities in real-time.