CVE-2018-7559 in UA .NET Standard
Summary
by MITRE
An issue was discovered in OPC UA .NET Standard Stack and Sample Code before GitHub commit 2018-04-12, and OPC UA .NET Legacy Stack and Sample Code before GitHub commit 2018-03-13. A vulnerability in OPC UA applications can allow a remote attacker to determine a Server's private key by sending carefully constructed bad UserIdentityTokens as part of an oracle attack.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 03/27/2023
The vulnerability identified as CVE-2018-7559 represents a critical security flaw in OPC UA implementations that affects both the .NET Standard Stack and Legacy Stack versions. This vulnerability specifically targets the authentication mechanisms within OPC UA applications and exposes a fundamental weakness in how these systems handle user identity tokens. The flaw allows remote attackers to perform oracle attacks against OPC UA servers, potentially compromising the confidentiality of sensitive cryptographic materials. The vulnerability was present in versions prior to specific GitHub commits, indicating that the issue was addressed through targeted code modifications that strengthened the authentication validation processes. This type of vulnerability is particularly concerning in industrial control systems where OPC UA is extensively deployed for communication between devices and control systems.
The technical nature of this vulnerability stems from insufficient validation of UserIdentityTokens within the OPC UA protocol implementation. When an attacker sends carefully crafted malformed or invalid UserIdentityTokens to the server, the system's response behavior reveals information about the server's internal state, including potentially exposing the private key used for cryptographic operations. This oracle attack pattern relies on the server's differential responses to valid and invalid authentication attempts, where the subtle differences in processing time, error messages, or response patterns provide attackers with enough information to gradually reconstruct the private key through mathematical analysis. The vulnerability demonstrates a classic example of information leakage through side-channel attacks that can be exploited to compromise the entire cryptographic infrastructure of the OPC UA server implementation.
The operational impact of this vulnerability extends beyond simple credential compromise, as it fundamentally undermines the security foundation of OPC UA-based industrial systems. Organizations relying on these protocols for critical infrastructure control face significant risks including unauthorized access to industrial processes, potential disruption of operations, and exposure of sensitive operational data. The vulnerability affects systems where OPC UA is used for secure communication between industrial devices, human machine interfaces, and enterprise systems, making it particularly dangerous in environments such as manufacturing plants, power generation facilities, and other critical infrastructure sectors. The ability to extract private keys through remote means removes the cryptographic protection that OPC UA is designed to provide, potentially allowing attackers to impersonate legitimate systems or decrypt sensitive communications.
Mitigation strategies for CVE-2018-7559 should focus on immediate patching of affected OPC UA implementations to the versions that include the security fixes introduced after the specified GitHub commits. Organizations should also implement additional monitoring and logging mechanisms to detect unusual authentication patterns that might indicate oracle attack attempts. Network segmentation and access controls should be strengthened to limit exposure of OPC UA servers to untrusted networks, while regular security assessments of industrial control systems should be conducted to identify similar vulnerabilities. The vulnerability aligns with CWE-200 (Information Exposure) and represents a specific instance of how improper error handling can lead to cryptographic key exposure, making it relevant to ATT&CK techniques involving credential access and privilege escalation. System administrators should also consider implementing additional authentication layers and regularly rotating cryptographic keys to minimize the impact of potential compromise, while maintaining detailed audit trails to support forensic analysis in case of security incidents.