CVE-2016-1296 in Web Security Appliance
Summary
by MITRE
The proxy engine on Cisco Web Security Appliance (WSA) devices with software 8.5.3-055, 9.1.0-000, and 9.5.0-235 allows remote attackers to bypass intended proxy restrictions via a malformed HTTP method, aka Bug ID CSCux00848.
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Analysis
by VulDB Data Team • 07/05/2022
The vulnerability described in CVE-2016-1296 represents a critical security flaw within Cisco Web Security Appliance (WSA) devices that affects specific software versions including 8.5.3-055, 9.1.0-000, and 9.5.0-235. This issue resides within the proxy engine component of the WSA platform, which serves as the core functionality for filtering and inspecting web traffic passing through the appliance. The vulnerability stems from an insufficient validation mechanism that fails to properly handle malformed HTTP methods, creating a pathway for unauthorized access that circumvents the intended security controls. The flaw specifically impacts the appliance's ability to enforce proxy restrictions, allowing malicious actors to bypass content filtering policies and access restricted resources that should be blocked by the security infrastructure.
The technical nature of this vulnerability falls under the category of improper input validation, which aligns with CWE-20 - Improper Input Validation. The proxy engine in Cisco WSA devices is designed to process HTTP requests and enforce security policies based on the method used in these requests. However, when a malformed HTTP method is submitted, the system fails to properly validate or reject the request, enabling attackers to craft specially formatted requests that exploit this weakness. The attack vector is remote, meaning that malicious actors can exploit this vulnerability without requiring physical access to the device or direct network connection to the appliance itself. The flaw essentially allows attackers to manipulate the proxy behavior by sending HTTP requests with non-standard method names that the appliance does not properly handle, leading to the bypass of access controls that should prevent unauthorized network access.
The operational impact of this vulnerability is significant as it directly undermines the core security function of the Cisco WSA appliance. Organizations relying on these devices for web content filtering, malware protection, and access control policies face a substantial risk of unauthorized network access and potential data breaches. The bypass of proxy restrictions means that malicious users could access blocked websites, download malicious content, or exploit vulnerabilities in applications that should be restricted by the security infrastructure. This vulnerability particularly affects enterprise environments where the WSA is used to enforce corporate web usage policies, protect against malware, and maintain compliance with security standards. The implications extend beyond simple content filtering as the bypass could enable more sophisticated attacks such as command execution, data exfiltration, or lateral movement within the network infrastructure.
Organizations should implement immediate mitigations including applying the relevant Cisco security patches and updates that address this specific vulnerability. The recommended approach involves upgrading the affected WSA software to versions that contain the necessary fixes for the HTTP method validation issue. Network administrators should also consider implementing additional monitoring and logging mechanisms to detect anomalous HTTP traffic patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation in security-critical systems and highlights the need for comprehensive testing of proxy engines against malformed inputs. Security teams should review their existing access control policies and ensure that alternative security measures are in place to protect against potential exploitation while patches are being deployed. This vulnerability also underscores the necessity of maintaining current security software versions and following vendor security advisories to prevent similar issues that could compromise network security infrastructure.