CVE-2020-3187 in ASA
Summary
by MITRE
A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to conduct directory traversal attacks and obtain read and delete access to sensitive files on a targeted system. The vulnerability is due to a lack of proper input validation of the HTTP URL. An attacker could exploit this vulnerability by sending a crafted HTTP request containing directory traversal character sequences. An exploit could allow the attacker to view or delete arbitrary files on the targeted system. When the device is reloaded after exploitation of this vulnerability, any files that were deleted are restored. The attacker can only view and delete files within the web services file system. This file system is enabled when the affected device is configured with either WebVPN or AnyConnect features. This vulnerability can not be used to obtain access to ASA or FTD system files or underlying operating system (OS) files. Reloading the affected device will restore all files within the web services file system.
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Analysis
by VulDB Data Team • 08/12/2026
The vulnerability identified as CVE-2020-3187 represents a critical directory traversal flaw within the web services interface of Cisco Adaptive Security Appliance (ASA) and Cisco Firepower Threat Defense (FTD) software products. This weakness stems from insufficient input validation mechanisms applied to HTTP Uniform Resource Locator (URL) parameters, creating an exploitable condition that allows remote attackers to manipulate file access requests. The vulnerability specifically affects systems where the web services functionality is enabled through either WebVPN or AnyConnect configuration features, making it particularly relevant for organizations utilizing these security solutions for remote access management. The flaw operates at the application layer of the network security infrastructure, potentially compromising the integrity and confidentiality of sensitive data stored within the web services file system.
The technical implementation of this vulnerability leverages standard directory traversal attack vectors by incorporating malicious character sequences such as "../" or similar path manipulation techniques within HTTP requests. When an attacker crafts a specially formatted request containing these traversal sequences, the system fails to properly validate or sanitize the input before processing the file access operation. This allows the malicious request to traverse the file system directory structure and access files that should normally be restricted to authorized users only. The vulnerability's impact is specifically scoped to the web services file system, meaning that while attackers can read and delete files within this designated area, they cannot access core system files or underlying operating system components. This limitation, while constraining the attack surface, still represents a significant security risk given that the web services file system may contain sensitive configuration data, user credentials, or other confidential information.
From an operational standpoint, this vulnerability creates substantial risk for organizations deploying Cisco ASA or FTD devices in their network security infrastructure. The unauthenticated nature of the attack means that any individual with network access can potentially exploit this flaw without requiring valid credentials or prior access to the system. The ability to delete files presents a potential for both data loss and service disruption, particularly if critical configuration files or certificates are removed from the web services file system. Additionally, the fact that deleted files are restored upon device reload creates a false sense of security for administrators while simultaneously providing attackers with a method to repeatedly attempt exploitation without permanent damage to the system. This characteristic also makes forensic analysis more challenging, as the deletion timestamps and evidence of compromise may not persist across system restarts.
Security professionals should consider this vulnerability in the context of the MITRE ATT&CK framework, where it aligns with techniques related to credential access and privilege escalation through application exploitation. The vulnerability maps to CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal. Organizations should implement immediate mitigation strategies including disabling unnecessary web services features when not actively required, implementing network segmentation to limit access to affected devices, and applying the latest security patches provided by Cisco. The vulnerability's exploitation requires minimal technical skill, making it particularly dangerous as it could be leveraged by attackers with basic knowledge of web application security. Network monitoring should be enhanced to detect unusual HTTP request patterns containing directory traversal sequences, and regular security assessments should verify that the web services file system contains only necessary files with appropriate access controls. Additionally, organizations should consider implementing additional authentication mechanisms and access controls for web services interfaces to further reduce the risk of unauthorized access to sensitive files within the affected file system.