CVE-2019-1920 in IOS Access Point
Summary
by MITRE
A vulnerability in the 802.11r Fast Transition (FT) implementation for Cisco IOS Access Points (APs) Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected interface. The vulnerability is due to a lack of complete error handling condition for client authentication requests sent to a targeted interface configured for FT. An attacker could exploit this vulnerability by sending crafted authentication request traffic to the targeted interface, causing the device to restart unexpectedly.
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Analysis
by VulDB Data Team • 11/01/2023
The vulnerability described in CVE-2019-1920 represents a critical flaw in the 802.11r Fast Transition implementation within Cisco IOS Access Points, specifically affecting wireless network infrastructure that relies on this standard for seamless roaming between access points. This issue manifests as a denial of service condition that can be triggered by an unauthenticated attacker positioned within the physical proximity of the targeted wireless interface. The vulnerability stems from insufficient error handling mechanisms during client authentication processes, creating a pathway for malicious actors to disrupt network operations through carefully crafted authentication requests. The 802.11r standard is designed to enable rapid and seamless handoff of wireless clients between access points while maintaining network connectivity, making this flaw particularly concerning for enterprise wireless environments where uninterrupted service is critical. The flaw specifically impacts the authentication request processing within the Fast Transition framework, where the system fails to properly handle certain error conditions that occur during client authentication procedures.
The technical nature of this vulnerability aligns with CWE-20, "Improper Input Validation," and CWE-399, "Resource Management Errors," as the system does not adequately validate incoming authentication requests or properly manage resources during the authentication process. When an attacker sends crafted authentication traffic to an interface configured for Fast Transition, the device's failure to properly handle the error conditions causes the system to enter an unstable state that ultimately results in an unexpected restart of the affected interface. This behavior demonstrates a classic resource exhaustion or state management failure where the system's inability to gracefully handle malformed or unexpected input leads to system instability. The vulnerability is particularly dangerous because it requires minimal privileges to exploit, as the attacker does not need authentication credentials to trigger the condition, and the attack can be executed from adjacent physical locations where wireless signals can reach the targeted access point. The impact is immediate and severe, as the restart of the wireless interface creates a complete disruption of service for all connected clients on that specific interface.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader network reliability concerns for organizations relying on Cisco wireless infrastructure. When an access point interface restarts unexpectedly, all wireless clients connected to that interface lose connectivity and must reassociate with available access points, potentially causing service interruptions for critical applications that depend on continuous wireless connectivity. The vulnerability affects the availability aspect of the CIA triad, specifically targeting the availability of wireless network services through deliberate disruption of the authentication process. Organizations with large wireless deployments may experience cascading effects as multiple interfaces restart simultaneously, leading to widespread service degradation across their wireless network infrastructure. The vulnerability also presents challenges for network monitoring and incident response teams, as the restart behavior can mask other underlying issues and complicate troubleshooting efforts. This type of denial of service attack can be particularly disruptive in mission-critical environments such as healthcare facilities, financial institutions, or industrial control systems where wireless connectivity is essential for operations.
Mitigation strategies for CVE-2019-1920 should focus on both immediate defensive measures and long-term architectural improvements to protect wireless infrastructure from such attacks. Network administrators should implement the latest Cisco IOS software updates that address the vulnerability, as these patches typically include enhanced error handling mechanisms for authentication requests within the Fast Transition framework. Physical security measures such as implementing proper wireless access point placement and using directional antennas can help reduce the attack surface by limiting an attacker's ability to position themselves within the effective range of targeted interfaces. Network segmentation strategies should be employed to isolate wireless interfaces that are particularly critical, ensuring that a single interface failure does not compromise the entire wireless network. Additionally, implementing robust monitoring and alerting systems that can detect unusual restart patterns or authentication traffic anomalies can help identify potential exploitation attempts before they cause significant service disruption. Organizations should also consider implementing rate limiting or traffic filtering mechanisms at the network perimeter to reduce the impact of crafted authentication requests. The vulnerability's exploitation aligns with ATT&CK technique T1499.001, "Network Denial of Service," and may also involve T1059.001, "Command and Scripting Interpreter," if attackers attempt to automate the exploitation process through scripting or automated tools. Regular vulnerability assessments and penetration testing of wireless infrastructure should be conducted to identify and remediate similar implementation flaws that could potentially be exploited in the future.