CVE-2018-0410 in AsyncOS
Summary
by MITRE
A vulnerability in the web proxy functionality of Cisco AsyncOS Software for Cisco Web Security Appliances could allow an unauthenticated, remote attacker to exhaust system memory and cause a denial of service (DoS) condition on an affected system. The vulnerability exists because the affected software improperly manages memory resources for TCP connections to a targeted device. An attacker could exploit this vulnerability by establishing a high number of TCP connections to the data interface of an affected device via IPv4 or IPv6. A successful exploit could allow the attacker to exhaust system memory, which could cause the system to stop processing new connections and result in a DoS condition. System recovery may require manual intervention. Cisco Bug IDs: CSCvf36610.
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Analysis
by VulDB Data Team • 05/02/2023
The vulnerability identified as CVE-2018-0410 represents a critical memory exhaustion flaw within Cisco AsyncOS Software that specifically targets the web proxy functionality of Cisco Web Security Appliances. This weakness stems from improper memory resource management during TCP connection handling, creating a pathway for unauthenticated remote attackers to exploit the system through deliberate resource depletion. The vulnerability manifests when the affected software fails to adequately manage memory allocation for TCP connections, leading to progressive memory consumption that ultimately results in system exhaustion. The attack vector leverages the ability to establish numerous TCP connections to the device's data interface, utilizing either IPv4 or IPv6 protocols to maximize connection throughput and memory consumption. This flaw fundamentally undermines the appliance's ability to maintain operational stability and service availability.
The technical implementation of this vulnerability operates through a memory management deficiency that allows attackers to consume system resources at an accelerated rate without proper connection limiting or resource accounting. When an attacker establishes a high volume of TCP connections, the system's memory allocation mechanisms become overwhelmed as each connection consumes memory resources without adequate cleanup or resource recycling. The vulnerability specifically targets the data interface of the web security appliance, which serves as the primary entry point for proxy traffic and connection handling. This targeted approach enables attackers to focus their resource exhaustion efforts on the most critical system components, maximizing the impact of their attack while minimizing the complexity of exploitation. The improper handling of TCP connection states creates a memory leak scenario where allocated resources are not properly released back to the system, leading to progressive degradation of available memory.
The operational impact of CVE-2018-0410 extends beyond simple service disruption to encompass complete system incapacitation and potential business continuity implications. When system memory becomes exhausted, the appliance ceases to process new connections effectively, resulting in a denial of service condition that affects all legitimate users of the web security services. The DoS condition can persist until manual system intervention occurs, requiring administrators to perform restart procedures or memory cleanup operations to restore normal functionality. This vulnerability directly relates to CWE-400, which addresses "Uncontrolled Resource Consumption" in software systems, and represents a classic example of resource exhaustion attacks that have been documented in various security frameworks including those referenced by the ATT&CK framework under network denial of service techniques. The attack requires minimal privileges and can be executed remotely, making it particularly dangerous for network security infrastructure components.
Mitigation strategies for this vulnerability should focus on implementing connection rate limiting and memory management controls to prevent excessive resource consumption. Network administrators should configure connection limits on the affected appliances to restrict the number of concurrent TCP connections that can be established, thereby preventing attackers from exhausting system resources through connection flooding. The implementation of proper TCP connection tracking and cleanup mechanisms can help ensure that memory allocated for connection states is properly released when connections are terminated. Additionally, network segmentation and access control measures should be implemented to limit exposure of the affected appliances to untrusted networks, reducing the attack surface available to potential adversaries. Cisco has addressed this vulnerability through software updates and patches that improve memory management and connection handling within the AsyncOS software, requiring administrators to apply these updates promptly to maintain system security and availability. The vulnerability demonstrates the importance of proper resource management in security appliances and highlights the need for robust memory handling mechanisms in all network infrastructure components that process external connections.