CVE-2017-6727 in Wide Area Application Services
Summary
by MITRE
A vulnerability in the Server Message Block (SMB) protocol of Cisco Wide Area Application Services (WAAS) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device due to a process restarting unexpectedly and creating Core Dump files. More Information: CSCvc63035. Known Affected Releases: 6.2(3a). Known Fixed Releases: 6.3(0.167) 6.2(3c)5 6.2(3.22).
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Analysis
by VulDB Data Team • 12/31/2020
The vulnerability identified as CVE-2017-6727 resides within the Server Message Block protocol implementation of Cisco Wide Area Application Services devices, representing a significant security weakness that enables remote attackers to execute denial of service attacks without requiring authentication. This flaw specifically impacts the WAAS platform's handling of SMB protocol communications, creating a condition where malicious actors can trigger unexpected process restarts that subsequently generate core dump files on the affected system. The issue stems from inadequate input validation and error handling mechanisms within the SMB processing code, which fails to properly manage malformed or unexpected protocol messages that could originate from external network sources.
The technical exploitation of this vulnerability occurs through carefully crafted SMB protocol requests that cause the WAAS device to enter an unstable state where critical processes restart automatically. These restarts generate core dump files that consume significant system resources and storage space, ultimately leading to the device becoming unresponsive or completely unavailable to legitimate users. The process restarts are not merely temporary disruptions but represent a fundamental failure in the device's ability to maintain operational stability when processing external network traffic. The core dump generation aspect of this vulnerability is particularly concerning as it can rapidly consume available disk space and memory resources, creating cascading failures that affect the entire device's operational capacity.
From an operational impact perspective, this vulnerability represents a serious threat to network availability and business continuity, particularly in environments where WAAS devices serve as critical infrastructure components for application delivery and optimization. The remote nature of the attack means that adversaries can exploit this weakness from anywhere on the network without requiring physical access or valid credentials, making it particularly dangerous for organizations that rely on WAAS for critical application performance. The DoS condition created by this vulnerability can persist until manual intervention occurs to clear core dump files and restart the affected services, potentially resulting in extended downtime that impacts user productivity and service availability.
Organizations affected by CVE-2017-6727 should prioritize immediate remediation through the application of available patches and updates, with the fixed releases 6.3(0.167), 6.2(3c)5, and 6.2(3.22) providing the necessary code modifications to address the underlying SMB processing flaws. The vulnerability aligns with CWE-20, "Improper Input Validation," and represents a classic example of how insufficient error handling in network protocols can lead to system instability. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique of "Endpoint Denial of Service" and demonstrates how protocol-level weaknesses can be leveraged to create persistent availability issues that require system-level intervention to resolve.
The remediation strategy should include comprehensive network segmentation to limit exposure of WAAS devices to untrusted networks, along with implementing network access controls that restrict SMB protocol access to only authorized sources. Security monitoring should be enhanced to detect unusual core dump file generation patterns that may indicate exploitation attempts, while regular system health checks should be implemented to identify potential DoS conditions before they escalate. Additionally, organizations should consider implementing intrusion detection systems that can identify suspicious SMB protocol traffic patterns that may precede exploitation attempts, providing early warning capabilities to prevent successful attacks from occurring.