CVE-2020-3582: Cisco Firepower Threat Defense XSS Flaw

CVE-2020-3582 Overview

Multiple cross-site scripting (XSS) vulnerabilities exist in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software. These vulnerabilities could allow an unauthenticated, remote attacker to conduct XSS attacks against users of the web services interface of an affected device. The vulnerabilities stem from insufficient validation of user-supplied input by the web services interface of an affected device. An attacker could exploit these vulnerabilities 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 access sensitive, browser-based information.

Critical Impact

Successful exploitation enables attackers to execute arbitrary JavaScript in the context of authenticated user sessions, potentially leading to session hijacking, credential theft, and unauthorized access to sensitive security infrastructure management interfaces.

Affected Products

• Cisco Adaptive Security Appliance (ASA) Software
• Cisco Firepower Threat Defense (FTD) Software
• Specific AnyConnect and WebVPN configurations (see Cisco advisory for details)

Discovery Timeline

• October 21, 2020 - CVE-2020-3582 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-3582

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting (XSS). The web services interface of affected Cisco ASA and FTD devices fails to properly sanitize user-supplied input before incorporating it into dynamically generated web pages. This allows attackers to inject malicious script code that executes within the security context of the victim's browser session.

The vulnerability affects the web-based management interface and VPN-related web services, which are critical components for remote access and device administration. Since these interfaces often handle sensitive authentication credentials and administrative functions, successful exploitation poses significant risks to network security infrastructure.

Root Cause

The root cause of CVE-2020-3582 lies in insufficient input validation within the web services interface. When user-supplied data is processed by the affected components, the application fails to properly encode or sanitize special characters that have significance in HTML and JavaScript contexts. This allows attackers to inject executable script content that is then reflected back to users or stored for later execution.

The vulnerability specifically affects certain AnyConnect and WebVPN configurations, indicating that the input validation deficiency is present in the code paths handling these particular features rather than the entire web interface.

Attack Vector

The attack is conducted remotely over the network and requires user interaction. An attacker must craft a malicious URL containing the XSS payload and persuade an authenticated user of the web services interface to click on the link. This is typically accomplished through social engineering techniques such as phishing emails or embedding malicious links in compromised websites.

Upon clicking the crafted link, the victim's browser executes the attacker's malicious script in the context of the legitimate Cisco web interface session. This grants the attacker the ability to perform actions on behalf of the victim, steal session tokens, capture credentials, or redirect users to malicious sites.

Detection Methods for CVE-2020-3582

Indicators of Compromise

• Unusual URL parameters containing JavaScript code or HTML tags in web server logs related to the ASA/FTD web interface
• Unexpected outbound connections from administrative workstations following access to the ASA/FTD management interface
• Reports from users of unexpected behavior when accessing VPN or management portals

Detection Strategies

• Monitor web server access logs for requests containing suspicious script tags, event handlers, or encoded JavaScript payloads
• Implement web application firewall (WAF) rules to detect and block common XSS payload patterns targeting the management interface
• Deploy browser-based security controls to detect attempts to exfiltrate session cookies or credentials

Monitoring Recommendations

• Enable detailed logging on the ASA/FTD web services interface and forward logs to a SIEM for analysis
• Configure alerting for anomalous authentication patterns or administrative actions following web interface access
• Review network traffic for suspicious redirects or connections to unknown external domains originating from administrator workstations

How to Mitigate CVE-2020-3582

Immediate Actions Required

• Apply the security patches provided by Cisco as documented in the Cisco Security Advisory
• Review and audit current AnyConnect and WebVPN configurations to determine if affected features are in use
• Implement network segmentation to restrict access to the web management interface to authorized administrative networks only

Patch Information

Cisco has released software updates that address these vulnerabilities. Administrators should consult the Cisco Security Advisory for detailed information on fixed software versions and upgrade paths. The advisory provides specific guidance on which software releases contain the security fixes for affected ASA and FTD deployments.

Workarounds

• Restrict web services interface access to trusted networks using access control lists (ACLs) to limit exposure
• Disable unnecessary WebVPN or AnyConnect portal features if they are not required for operations
• Educate users with access to the management interface about phishing risks and the importance of verifying link authenticity before clicking