CVE-2017-6628 in Wide Area Application Services
Summary
by MITRE
A vulnerability in SMART-SSL Accelerator functionality for Cisco Wide Area Application Services (WAAS) 6.2.1, 6.2.1a, and 6.2.3a could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition where the WAN optimization could stop functioning while the process restarts. The vulnerability is due to a Secure Sockets Layer/Transport Layer Security (SSL/TLS) alert being incorrectly handled when in a specific SSL/TLS connection state. An attacker could exploit this vulnerability by establishing a SMART-SSL connection through the targeted device. The attacker would then send a crafted stream of SSL/TLS traffic. An exploit could allow the attacker to cause a DoS condition where WAN optimization could stop processing traffic for a short period of time. Cisco Bug IDs: CSCvb71133.
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Analysis
by VulDB Data Team • 12/22/2020
The vulnerability identified as CVE-2017-6628 resides within the SMART-SSL Accelerator functionality of Cisco Wide Area Application Services (WAAS) versions 6.2.1, 6.2.1a, and 6.2.3a, representing a critical security flaw that enables unauthenticated remote attackers to disrupt network services through deliberate denial of service attacks. This vulnerability specifically targets the handling of Secure Sockets Layer/Transport Layer Security protocols within the WAAS appliance, creating a condition where the system becomes temporarily non-functional during the restart process. The flaw manifests when the system incorrectly processes SSL/TLS alerts while in a specific connection state, fundamentally undermining the reliability of WAN optimization services that organizations depend upon for network performance management.
The technical implementation of this vulnerability stems from improper state management within the SSL/TLS processing pipeline of the WAAS appliance, which falls under CWE-248, an unspecified CWE category that encompasses improper exception handling in protocols. When an attacker establishes a SMART-SSL connection and subsequently sends a carefully crafted stream of SSL/TLS traffic, the system's failure to properly handle the specific SSL/TLS alert conditions triggers an unexpected state transition that leads to service disruption. This behavior aligns with ATT&CK technique T1499.004, which involves network disruption attacks targeting availability through protocol manipulation. The vulnerability's exploitation requires minimal privileges since no authentication is necessary, making it particularly dangerous as it can be leveraged by any remote attacker without requiring access credentials or network privileges.
The operational impact of this vulnerability extends beyond simple service interruption, as it directly affects the core functionality of WAN optimization services that organizations rely on for efficient network resource utilization and application performance. When the DoS condition occurs, the WAAS appliance ceases processing traffic for a brief but critical period, potentially causing network latency issues, application slowdowns, and service degradation across distributed networks. The restart process that follows the attack can further compound the disruption, as the appliance must recover from the failed SSL/TLS state handling, potentially affecting multiple concurrent connections and network optimization tasks. This vulnerability particularly impacts enterprise networks that depend on WAAS for bandwidth optimization and application acceleration, where even brief service interruptions can result in significant business impact.
Organizations affected by this vulnerability should prioritize immediate mitigation through official Cisco security advisories and patches, as the vulnerability represents a clear risk to network availability and service continuity. The recommended approach involves applying the appropriate software updates that address the SSL/TLS state handling anomalies within the SMART-SSL Accelerator functionality. Additionally, network administrators should implement monitoring solutions to detect unusual SSL/TLS traffic patterns that might indicate exploitation attempts, while also considering network segmentation strategies to limit the potential impact of such attacks. The vulnerability demonstrates the importance of proper protocol implementation and state management in network security appliances, as highlighted by the ATT&CK framework's emphasis on maintaining system availability through proper handling of network protocols and connection states.