CVE-2000-0178 in ServerIron
Summary
by MITRE
ServerIron switches by Foundry Networks have predictable TCP/IP sequence numbers, which allows remote attackers to spoof or hijack sessions.
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Analysis
by VulDB Data Team • 04/20/2026
The ServerIron series of network switches manufactured by Foundry Networks contained a critical security vulnerability that fundamentally compromised the integrity of TCP communications passing through these devices. This vulnerability manifested in the predictable generation of TCP sequence numbers, a flaw that directly undermined the security mechanisms designed to prevent session hijacking and man-in-the-middle attacks. The issue affected network infrastructure components that were widely deployed in enterprise and service provider environments, making it particularly concerning from a cybersecurity perspective.
The technical flaw centered on the switch's inability to generate cryptographically secure random numbers for TCP sequence number initialization. Instead of utilizing proper randomization techniques that would make sequence number prediction computationally infeasible, the ServerIron switches employed deterministic or poorly randomized algorithms that allowed attackers to forecast future sequence numbers. This weakness specifically impacted the TCP/IP stack implementation within the switch's network processing engine, where sequence numbers are crucial for maintaining connection state and ensuring data integrity. The vulnerability was classified as a weakness in random number generation, aligning with CWE-330, which addresses the use of insufficiently random values in security contexts.
The operational impact of this vulnerability was severe and far-reaching, as it enabled remote attackers to perform session hijacking attacks without requiring local access or sophisticated reconnaissance. An attacker positioned in the network path could exploit the predictable sequence numbers to inject malicious data into active TCP sessions, effectively taking control of network communications between legitimate endpoints. This capability extended beyond simple data interception to include complete session takeover, allowing attackers to impersonate legitimate users and systems. The vulnerability was particularly dangerous because it affected the core networking infrastructure rather than individual endpoints, making it difficult to detect and isolate. The attack vector required only network access and knowledge of the target communication patterns, making it accessible to attackers with moderate technical skills.
Mitigation strategies for this vulnerability required immediate action from network administrators, including firmware updates from Foundry Networks that addressed the random number generation algorithm. Organizations needed to implement network segmentation and additional security controls to limit the attack surface, as the vulnerability could be exploited from any position in the network path. Network monitoring solutions were essential for detecting anomalous TCP behavior that might indicate exploitation attempts. The incident highlighted the importance of cryptographic security in network infrastructure components and led to enhanced security requirements for embedded systems. From a strategic perspective, this vulnerability reinforced the need for comprehensive security testing of network equipment and the implementation of defense-in-depth strategies that protect against both external and internal threats. The vulnerability also demonstrated the critical relationship between network infrastructure security and overall enterprise security posture, as compromised switches could provide attackers with persistent access to network resources. This case study became a foundational example in understanding how seemingly minor implementation flaws in network devices could result in significant security breaches affecting entire network infrastructures.