CVE-1999-0430 in Catalyst 5000
Summary
by MITRE
Cisco Catalyst LAN switches running Catalyst 5000 supervisor software allows remote attackers to perform a denial of service by forcing the supervisor module to reload.
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Analysis
by VulDB Data Team • 04/18/2026
The vulnerability identified as CVE-1999-0430 affects Cisco Catalyst 5000 series LAN switches that operate with specific supervisor software versions. This weakness represents a significant security flaw in network infrastructure equipment that could be exploited by remote attackers to disrupt critical network operations. The vulnerability specifically targets the supervisor module of these switches, which serves as the central control unit responsible for managing switch operations and maintaining system stability. The affected Cisco Catalyst 5000 series switches are widely deployed in enterprise and corporate network environments where reliable network connectivity is paramount for business operations.
The technical flaw in this vulnerability stems from inadequate input validation and error handling within the supervisor software's processing mechanisms. When remote attackers send specifically crafted network packets or commands to the switch, the supervisor module fails to properly handle these inputs, leading to a condition that forces the entire supervisor module to reboot or reload. This occurs due to the absence of proper bounds checking and validation procedures in the software's network processing routines, which allows malicious input to trigger unexpected system behavior. The vulnerability is classified as a denial of service condition that can be triggered remotely without requiring authentication or specialized access privileges, making it particularly dangerous in network environments where such switches are exposed to untrusted network traffic.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network reliability and business continuity. When the supervisor module reloads, the switch loses its configuration and must reinitialize its network operations, which can result in temporary network outages that affect multiple users and applications. In enterprise environments where the Catalyst 5000 switches serve as core network infrastructure components, such disruptions can cascade across multiple network segments and impact critical business applications. The remote exploitability of this vulnerability means that attackers can potentially cause repeated disruptions without needing physical access to the network equipment, creating a persistent threat to network availability. This type of vulnerability aligns with CWE-122 which describes improper handling of input data leading to buffer overflows or similar conditions that can cause system instability.
Organizations affected by this vulnerability should implement immediate mitigations to protect their network infrastructure from potential exploitation. The primary recommendation involves applying the latest security patches and firmware updates provided by Cisco to address the underlying software flaws in the supervisor module. Network administrators should also consider implementing access control measures such as firewall rules or network segmentation to limit exposure of these switches to untrusted network traffic. Monitoring network traffic for suspicious patterns or malformed packets that could indicate exploitation attempts is crucial for early detection of potential attacks. Additionally, implementing redundant network paths and backup systems can help maintain service availability during potential exploitation events. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1499 which involves the use of denial of service attacks against network infrastructure to disrupt operations and compromise availability.
The broader implications of this vulnerability highlight the importance of secure software development practices in network infrastructure equipment. It underscores the need for comprehensive testing of input validation procedures and proper error handling mechanisms in network devices that operate in potentially hostile environments. Organizations should also consider implementing network monitoring solutions that can detect anomalous behavior patterns that may indicate exploitation attempts. The vulnerability serves as a reminder that network infrastructure components, even those considered critical for business operations, can contain fundamental flaws that create security risks when exposed to remote network traffic. Regular vulnerability assessments and security audits of network equipment are essential to identify and remediate similar weaknesses before they can be exploited by malicious actors.