A time-of-check time-of-use vulnerability in PulseSecureService.exe in Pulse Secure Client versions prior to 9.1.6 down to 5.3 R70 for Windows (which runs as NT AUTHORITY/SYSTEM) allows unprivileged users to run a Microsoft Installer executable with elevated privileges.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-13162
• https://github.com/sepcali
• https://kb.pulsesecure.net/?atype=sa
• https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44503
• https://twitter.com/gsepcali/status/1262551597990711296
• https://twitter.com/gsepcali/status/1272927080909623297
• https://twitter.com/sepcali
• https://twitter.com/sepcali/status/1262551277940211712
• https://twitter.com/sepcali/status/1262551336152948738
• https://twitter.com/sepcali/status/1262551597990711296
• https://www.redtimmy.com/privilege-escalation/pulse-secure-client-for-windows-9-1-6-toctou-privilege-escalation-cve-2020-13162/
• http://packetstormsecurity.com/files/158117/Pulse-Secure-Client-For-Windows-Local-Privilege-Escalation.html
• http://packetstormsecurity.com/files/159065/Pulse-Secure-Windows-Client-Privilege-Escalation.html
• http://seclists.org/fulldisclosure/2020/Jun/25
• http://seclists.org/fulldisclosure/2020/Sep/15