CVE-2015-0746 in Access Control Server
Summary
by MITRE
The REST API in Cisco Access Control Server (ACS) 5.5(0.46.2) allows remote attackers to cause a denial of service (API outage) by sending many requests, aka Bug ID CSCut62022.
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Analysis
by VulDB Data Team • 07/12/2017
The vulnerability identified as CVE-2015-0746 affects the REST API implementation within Cisco Access Control Server version 5.5(0.46.2), representing a significant security weakness that can be exploited to disrupt service availability. This issue manifests through a specific flaw in how the system handles concurrent API requests, creating a pathway for remote attackers to execute denial of service attacks against the access control infrastructure. The vulnerability operates under the broader category of resource exhaustion attacks, where malicious actors can overwhelm system resources through carefully crafted request patterns that strain the API processing capabilities.
The technical mechanism behind this vulnerability involves the REST API's inadequate handling of high-volume request scenarios, particularly when multiple concurrent requests are processed simultaneously. The system fails to implement proper rate limiting or request queuing mechanisms that would normally protect against such abuse patterns. This weakness allows attackers to flood the API with numerous requests in a short time frame, causing the system to become unresponsive or crash entirely. The underlying flaw can be categorized as a lack of input validation and resource management controls, which aligns with CWE-400, specifically addressing unchecked resource consumption. The vulnerability demonstrates poor defensive programming practices where the system does not adequately protect against excessive load conditions that could compromise availability.
From an operational impact perspective, this vulnerability poses a severe threat to organizations relying on Cisco ACS for access control management, as it can render the entire access control system unavailable to legitimate users. The denial of service condition affects not only the REST API but can potentially impact the broader access control infrastructure, causing cascading failures that disrupt network access and authentication services. Attackers can exploit this weakness without requiring authentication credentials, making the attack surface particularly dangerous as it can be executed from any network location. The impact extends beyond simple service disruption to potentially compromise security operations, as access control systems are fundamental to network security posture and identity management.
The exploitation of this vulnerability aligns with tactics documented in the MITRE ATT&CK framework under the technique of "Denial of Service" and specifically relates to the use of resource exhaustion as a method of attack. Organizations implementing Cisco ACS 5.5(0.46.2) should consider this vulnerability as part of their broader threat landscape, particularly in environments where network access control systems are critical to security operations. The vulnerability also highlights the importance of proper API security design and implementation practices, emphasizing the need for robust rate limiting, request monitoring, and resource management controls. Security teams should implement monitoring solutions to detect unusual request patterns that may indicate exploitation attempts, while also ensuring that system administrators maintain awareness of the specific vulnerability and its potential impact on access control operations.
Mitigation strategies should include immediate implementation of rate limiting controls on the REST API endpoints, deployment of network-based protections to filter excessive traffic patterns, and consideration of upgrading to patched versions of Cisco ACS that address the resource exhaustion vulnerability. Organizations should also establish monitoring procedures to track API usage patterns and detect potential abuse attempts before they can cause significant service disruption. The vulnerability underscores the critical importance of maintaining current security patches and implementing proper access control for API endpoints to prevent unauthorized exploitation of system resources.