CVE-2017-6751 in Web Security Appliance
Summary
by MITRE
A vulnerability in the web proxy functionality of the Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to forward traffic from the web proxy interface of an affected device to the administrative management interface of an affected device, aka an Access Control Bypass Vulnerability. Affected Products: virtual and hardware versions of Cisco Web Security Appliance (WSA). More Information: CSCvd88863. Known Affected Releases: 10.1.0-204 9.0.0-485.
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Analysis
by VulDB Data Team • 01/06/2021
The vulnerability identified as CVE-2017-6751 represents a critical access control bypass flaw within Cisco Web Security Appliance WSA systems that fundamentally undermines the device's security architecture. This weakness exists in the web proxy functionality of the appliance, creating a pathway for unauthenticated remote attackers to exploit a logical flaw in the device's network interface management. The vulnerability specifically targets the separation between the web proxy interface and the administrative management interface, which should normally be isolated to prevent unauthorized access to sensitive management functions. The flaw allows attackers to manipulate traffic routing through the web proxy interface to reach the administrative management interface, effectively bypassing the intended access controls that should prevent such cross-interface communication.
The technical implementation of this vulnerability stems from inadequate input validation and improper access control mechanisms within the WSA's proxy handling code. When processing network requests through the web proxy interface, the system fails to properly validate the destination of traffic flows, allowing maliciously crafted requests to redirect traffic to management interfaces that should remain protected from external access. This represents a classic case of insufficient access control enforcement, classified under CWE-284 Access Control Bypass. The vulnerability's exploitation requires no authentication credentials, making it particularly dangerous as attackers can leverage this flaw from any external network location without prior access to the device. The affected versions include both virtual and hardware deployments of the WSA platform, indicating that the flaw exists at the software level rather than being hardware-specific.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it provides attackers with the ability to potentially compromise the entire administrative management interface of affected appliances. This interface typically contains critical configuration settings, user management functions, and system monitoring capabilities that would normally be protected from external interference. Successful exploitation could enable attackers to modify security policies, disable protective features, access sensitive logs and reports, or even install malicious software on the appliance. The implications are particularly severe for organizations that rely on WSA appliances for network security enforcement, as this vulnerability essentially allows attackers to gain administrative control over their network traffic inspection and filtering capabilities. From an ATT&CK framework perspective, this vulnerability maps to T1078 Valid Accounts and T1068 Exploitation for Privilege Escalation, as it enables unauthorized access to administrative functions without proper authentication.
Organizations affected by this vulnerability should implement immediate mitigations including applying the relevant Cisco security patches, implementing network segmentation to isolate management interfaces from external access, and configuring additional access control lists to prevent cross-interface traffic. The Cisco advisory CSCvd88863 provides specific guidance on patch deployment and temporary workarounds that can be implemented while waiting for official security updates. Network administrators should also conduct thorough vulnerability assessments to identify any unauthorized access attempts that may have occurred during the period when the device was vulnerable. Additional monitoring should be implemented to detect unusual traffic patterns that might indicate exploitation attempts, particularly around the web proxy interface ports and management interface endpoints. The vulnerability highlights the critical importance of proper interface isolation and access control enforcement in network security appliances, and serves as a reminder of the potential consequences when these fundamental security principles are not properly implemented.