CVE-2020-3452: Cisco Adaptive Security Appliance and Firepower Threat Defense Path Traversal Vulnerability

After Cisco disclosed a serious vulnerability in its Adaptive Security Appliance and Firepower Threat Defense, one of the security researchers credited with its discovery released proof of concept code for the flaw.

Background

On July 22, Cisco published an advisory for a highly rated vulnerability in its Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) software used by the ASA family of devices that “protects corporate networks and data centers of all sizes.”

Discovery of the vulnerability is independently credited to three researchers: Mikhail Klyuchnikov of Positive Technologies, and Abdulrahman Nour and Ahmed Aboul-Ela of RedForce.

Analysis

CVE-2020-3452 is a read-only path traversal vulnerability in Cisco ASA and FTD software. A remote, unauthenticated attacker could exploit this vulnerability by sending a specially crafted HTTP request to a vulnerable system. Successful exploitation would allow the attacker to view sensitive information contained within files on the web services file system.

Cisco notes that an attacker would only be able to access these files when WebVPN or AnyConnect has been configured on the system. It is important to note that an attacker would not be able to read files from the ASA, FTD or underlying operating system, which limits the impact of this vulnerability and explains why it received a CVSSv3 score of 7.5.

Previously disclosed path traversal vulnerabilities

Klyuchnikov, who is one of the researchers credited with discovering CVE-2020-3452, has a history of discovering notable path traversal vulnerabilities. He previously discovered CVE-2019-19781, a critical vulnerability in Citrix Application Delivery Controller and Gateway devices, and more recently CVE-2020-5902, a critical vulnerability in the traffic management user interface (TMUI) of F5 BIG-IP devices.

As part of a news release for CVE-2020-3452 on the Positive Technologies website, Klyuchnikov calls this vulnerability “highly dangerous,” noting that an attacker would be able to “gain access to the file system (RamFS), which stores data in RAM.” As a result, an attacker could gain read-only privileges for WebVPN files, which include “the WebVPN configuration of Cisco ASA users, bookmarks, cookies, web content, and HTTP URL addresses.”

Proof of concept

Ahmed Aboul-Ela, one of the other researchers independently credited with discovering this vulnerability, published a series of tweets that included two proof-of-concept (PoC) code snippets for this flaw.

The first PoC targets the ASA translation table endpoint:

Here is POC of CVE-2020-3452, unauthenticated file read in Cisco ASA & Cisco Firepower.

For example to read "/+CSCOE+/portal_inc.lua" file.

https://<domain>/+CSCOT+/translation-table?type=mst&textdomain=/%2bCSCOE%2b/portal_inc.lua&default-language&lang=../

Happy Hacking! pic.twitter.com/aBA3R7akkC

— Ahmed Aboul-Ela (@aboul3la) July 22, 2020

The second PoC targets the ASA oem-customization endpoint:

I would also like to mention that there is another endpoint that's vulnerable to the same path traversal issue.

POC #2:
https://<domain>/+CSCOT+/oem-customization?app=AnyConnect&type=oem&platform=..&resource-type=..&name=%2bCSCOE%2b/portal_inc.lua

Enjoy! :) pic.twitter.com/ivBEaXFyDq

— Ahmed Aboul-Ela (@aboul3la) July 23, 2020

In both PoCs, Aboul-Ela exploits the vulnerability to read the “"/+CSCOE+/portal_inc.lua" file.

Solution

Cisco has released the following patches for both ASA and FTD:

Please note that Cisco ASA 9.5 and earlier and 9.7 have reached end of life and are no longer receiving security updates. Customers are advised to upgrade to a fixed version of ASA noted in the table above.

Cisco has also specified that hotfixes for affected FTD versions are available or will soon become available. They recommend customers running the affected versions of FTD could:

• Migrate to a newer version of FTD
• Apply the available or upcoming hotfixes
• Wait until the next FTD release is scheduled to be published

For more in-depth information, please visit the “Fixed Releases” section under Cisco’s advisory for CVE-2020-3452.

Identifying affected systems

A list of Tenable plugins to identify this vulnerability will appear here as they’re released.

Get more information

• Cisco Advisory for CVE-2020-3452
• Positive Technologies News Release for CVE-2020-3452
• Proof of Concept #1 for CVE-2020-3452
• Proof of Concept #2 for CVE-2020-3452

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