The Citrix vulnerability (CVE-2019-19781) was first identified in December of 2019. This vulnerability is a directory traversal attack that can lead to remote code execution. So far two directory traversals are needed to execute commands. One is in the URI and the other is with the NSC_USER: field in the HTTP Header.
The directory traversal allows access to the newbm.pl script. Through this script, commands can be injected into a new XML file pointed at by the NSC_USER field. After the commands have been successfully written, a simple GET request to the XML file will execute the commands.
Many proof of concept scripts are available as well as scanners to check and see if your system is vulnerable. As with many vulnerabilities that affect thousands of systems, we are seeing Crypto Miners taking advantage of it first.
POST Request with /vpn/../vpns/ and newbm.pl
NSC_USER with ../ in the Header
GET request after the above POST with /vpn/../vpns/ and an .xml file
Request to /vpn/../vpns/cfg/smb.conf (likely a scanner)
SHA256:
ff3c0cb8d31360699ec56f1b9f11aa86cb69649ac2f747cdd3b7893b04861f75
SHA1:
301c03b4f943757e1e275ffce13029d53c0f4053
MD5:
0e431d0d9e0fc371c163e4de5226c50b
SHA256:
20343854b8c348146bf17fe739ce9028a620f93116438291f1b0b89345e18520feccc
SHA1:
fecccb8a7274992fb76426457bb8a8cc76637d46
MD5:
08f76eb3d62d53bff131d2cb0af2773d
Below is a list of affected devices and the dates that Citrix expects to have a patch ready. There’s also a link to receive a notification once the patch is available.
The vulnerability affects all supported product versions and all supported platforms:
|
Version |
Refresh Build |
Expected Release Date |
|
10.5 |
10.5.70.x |
31st January 2020 |
|
11.1 |
11.1.63.x |
20th January 2020 |
|
12.0 |
12.0.63.x |
20th January 2020 |
|
12.1 |
12.1.55.x |
27th January 2020 |
|
13.0 |
13.0.47.x |
27th January 2020 |
Mitigation Steps:
https://support.citrix.com/article/CTX267679
Bulletin Alerts:
https://support.citrix.com/user/alerts