CVE-2015-3963 in VxWorks
Summary
by MITRE
Wind River VxWorks before 5.5.1, 6.5.x through 6.7.x before 6.7.1.1, 6.8.x before 6.8.3, 6.9.x before 6.9.4.4, and 7.x before 7 ipnet_coreip 1.2.2.0, as used on Schneider Electric SAGE RTU devices before J2 and other devices, does not properly generate TCP initial sequence number (ISN) values, which makes it easier for remote attackers to spoof TCP sessions by predicting an ISN value.
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Analysis
by VulDB Data Team • 06/07/2022
The vulnerability identified as CVE-2015-3963 affects Wind River VxWorks operating systems across multiple version ranges including 5.5.1, 6.5.x through 6.7.x, 6.8.x, 6.9.x, and 7.x, specifically within the ipnet_coreip component version 1.2.2.0. This issue impacts critical infrastructure devices such as Schneider Electric SAGE RTU devices before J2 and other embedded systems that rely on VxWorks for network communication. The flaw resides in the TCP initial sequence number generation mechanism, which is fundamental to TCP session establishment and security. According to CWE-310, this represents a weakness in cryptographic randomness or pseudo-random number generation, directly undermining the security of network communications. The vulnerability operates at the transport layer of the OSI model, specifically affecting TCP protocol implementation within embedded real-time operating systems.
The technical flaw stems from inadequate entropy in the generation of TCP initial sequence numbers, which are critical for establishing secure TCP connections. In a properly functioning TCP implementation, these sequence numbers should be unpredictable and uniformly distributed to prevent session hijacking attacks. However, the vulnerable VxWorks versions employ predictable or insufficiently random ISN generation algorithms, making it feasible for remote attackers to predict future sequence numbers. This vulnerability aligns with ATT&CK technique T1071.004 for Application Layer Protocol: DNS and T1566.001 for Phishing: Spearphishing Attachment, as attackers can leverage predictable ISNs to conduct session hijacking and man-in-the-middle attacks. The weakness essentially compromises the cryptographic foundation of TCP communication, allowing adversaries to forge TCP packets and impersonate legitimate network endpoints.
The operational impact of this vulnerability is significant for industrial control systems and embedded devices that rely on VxWorks for network connectivity. Attackers can exploit this weakness to perform TCP session hijacking, potentially gaining unauthorized access to critical systems controlling industrial processes, power grids, or other infrastructure. The vulnerability affects devices deployed in environments where network security is paramount, including SCADA systems, remote terminal units, and industrial automation equipment. Given that many of these systems operate in isolated networks without traditional security controls, the ability to predict ISNs and hijack sessions creates a severe risk of system compromise. The vulnerability also impacts the confidentiality, integrity, and availability of network communications, as attackers can intercept, modify, or disrupt data transmission between network endpoints.
Mitigation strategies for CVE-2015-3963 primarily involve upgrading affected VxWorks versions to patched releases, specifically targeting the ipnet_coreip component. Organizations should implement network segmentation and monitoring to detect anomalous TCP traffic patterns that might indicate session hijacking attempts. The use of TCP timestamps and other security extensions can help detect and prevent exploitation of predictable ISN values. Additionally, implementing network access controls, intrusion detection systems, and regular security assessments can provide defense-in-depth measures. According to NIST SP 800-53 controls, organizations should maintain updated system inventories and apply security patches promptly. The vulnerability also highlights the importance of secure coding practices and proper random number generation in embedded systems, aligning with CWE-338 and security frameworks such as ISO/IEC 27001. Regular vulnerability assessments and penetration testing should be conducted to identify similar weaknesses in other embedded systems and network protocols.