CVE-2017-6765 in ASA
Summary
by MITRE
A vulnerability in the web-based management interface of Cisco Adaptive Security Appliance (ASA) 9.1(6.11) and 9.4(1.2) could allow an unauthenticated, remote attacker to conduct a cross-site scripting (XSS) attack against a user of the web-based management interface of an affected device, aka WebVPN XSS. The vulnerability is due to insufficient validation of user-supplied input by the web-based management interface of an affected device. An attacker could exploit this vulnerability by persuading a user of the interface to click a crafted link. A successful exploit could allow the attacker to execute arbitrary script code in the context of the interface or allow the attacker to access sensitive browser-based information. Cisco Bug IDs: CSCve19179.
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Analysis
by VulDB Data Team • 01/07/2021
The vulnerability identified as CVE-2017-6765 represents a critical cross-site scripting flaw within the web-based management interface of Cisco Adaptive Security Appliance (ASA) devices running specific software versions. This weakness exists in ASA 9.1(6.11) and 9.4(1.2) releases, creating a significant security risk for organizations relying on these network security appliances. The vulnerability specifically affects the WebVPN functionality, which provides remote access capabilities to network resources through web-based interfaces. The flaw stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied data before processing, allowing malicious payloads to be injected and executed within the browser context of authenticated users.
The technical exploitation of this vulnerability occurs through a sophisticated social engineering attack vector where an attacker crafts a malicious link designed to exploit the insufficient input validation. When a legitimate user interacts with this crafted link through the web-based management interface, the malicious script code is executed within the user's browser session. This execution context allows the attacker to perform actions as if they were the authenticated user, potentially gaining access to sensitive browser-based information or executing arbitrary code within the security appliance's management interface. The vulnerability operates at the application layer and specifically targets the web interface components responsible for processing user input, making it particularly dangerous for administrators who regularly access the ASA management console.
The operational impact of this vulnerability extends beyond simple script execution, as it creates a potential pathway for attackers to escalate privileges and compromise the entire security appliance. An attacker who successfully exploits this vulnerability could gain unauthorized access to sensitive configuration data, modify security policies, or even establish persistent access to the network infrastructure. The remote nature of the attack means that threat actors do not require physical access or credentials to exploit this flaw, making it particularly concerning for organizations with remote management capabilities. This vulnerability directly aligns with CWE-79, which describes cross-site scripting flaws, and represents a classic example of how insufficient input validation can create persistent security risks in web applications. The attack pattern follows the typical methodology described in the ATT&CK framework under T1059.007 for script injection techniques, where adversaries leverage web application vulnerabilities to execute malicious code.
Organizations affected by this vulnerability should immediately implement multiple layers of defensive measures to protect their network infrastructure. The primary mitigation strategy involves applying the official Cisco security patches and updates released to address this specific XSS vulnerability, which would include updating the ASA software to versions that properly validate and sanitize user input. Network segmentation and access controls should be strengthened to limit exposure of the web-based management interface to only trusted administrative networks. Additionally, implementing web application firewalls and content security policies can provide additional protection against similar attacks. Regular monitoring of web interface access logs and user behavior analytics should be deployed to detect anomalous activities that might indicate exploitation attempts. Security awareness training for administrators should emphasize the importance of not clicking suspicious links and maintaining vigilance when accessing management interfaces, as the social engineering component of this attack relies heavily on user interaction with malicious payloads.