CVE-2019-1891 in Small Business 200 Managed Switch
Summary
by MITRE
A vulnerability in the web interface of Cisco Small Business 200, 300, and 500 Series Managed Switches could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper validation of requests sent to the web interface. An attacker could exploit this vulnerability by sending a malicious request to the web interface of an affected device. A successful exploit could allow the attacker to cause an unexpected reload of the device, resulting in a DoS condition.
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Analysis
by VulDB Data Team • 10/18/2023
The vulnerability identified as CVE-2019-1891 affects Cisco Small Business 200, 300, and 500 Series Managed Switches, representing a critical security flaw in the web interface component of these networking devices. This vulnerability stems from inadequate input validation mechanisms within the web server implementation, creating a pathway for malicious actors to disrupt network operations. The affected devices operate in small business environments where network reliability is paramount, making this vulnerability particularly concerning as it can be exploited remotely without requiring authentication credentials.
The technical flaw manifests through improper request validation within the web interface of these managed switches, specifically failing to adequately sanitize or verify incoming HTTP requests. When an attacker crafts and sends a maliciously formatted request to the web interface, the device's insufficient validation logic processes the malformed input without proper error handling or request filtering. This processing failure leads to an unexpected system state where the device undergoes an unintended reboot cycle, effectively causing a denial of service condition that disrupts network connectivity for all connected devices.
From an operational perspective, the impact of this vulnerability extends beyond simple network disruption as it can compromise business continuity for small organizations relying on these switches for their network infrastructure. The remote exploitation capability means that attackers can initiate the DoS condition from outside the local network perimeter, making the vulnerability particularly dangerous for organizations with limited security monitoring capabilities. Network administrators face the challenge of maintaining uptime while the vulnerability remains unpatched, potentially resulting in significant productivity losses and potential financial impact from extended network outages.
The vulnerability aligns with CWE-20, which describes "Improper Input Validation" as a fundamental weakness in software design where input data is not properly validated before being processed. This weakness creates a foundation for various attack vectors including denial of service conditions, as demonstrated in this Cisco vulnerability. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1499.004, "Endpoint Denial of Service," where attackers target network infrastructure devices to cause service disruption. The lack of authentication requirements for exploitation makes this particularly dangerous as it requires minimal attacker privileges to execute the attack, aligning with ATT&CK technique T1190, "Exploit Public-Facing Application," which specifically addresses vulnerabilities in externally accessible services.
Mitigation strategies should prioritize immediate deployment of Cisco's security patches and firmware updates addressing this vulnerability. Network administrators should also implement network segmentation to limit access to these devices, utilizing firewalls to restrict web interface access to trusted administrative networks only. Additional protective measures include disabling unnecessary web interface services when not actively required, implementing robust network monitoring to detect unusual reboot patterns, and maintaining detailed network logs to track access attempts. Regular vulnerability assessments and security audits of network infrastructure components should be conducted to identify similar validation weaknesses in other network devices within the organization's environment.