CVE-2019-16784: Local Privilege Escalation in PyInstaller

Local Privilege Escalation in all Windows software frozen by PyInstaller in “onefile” mode.

The vulnerability is present only on Windows and in this particular case: If a software frozen by PyInstaller in “onefile” mode is launched by a (privileged) user who has his/her “TempPath” resolving to a world writable directory. This is the case e.g. if the software is launched as a service or as a scheduled task using a system account (in which case TempPath will default to C:\Windows\Temp).

In order to be exploitable the software has to be (re)started after the attacker has launched the exploit program. So for a service launched at startup, a service restart is needed (e.g. after a crash or an upgrade).

While PyInstaller itself was not vulnerable, all Windows software frozen by PyInstaller in “onefile” mode is vulnerable.

CVSSv3 score 7.0 (High) CVSSv3 vector CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected

• all Windows software frozen by PyInstaller in “onefile” mode

No affected

• PyInstaller itself (except if frozen by PyInstaller in “onefile” mode on Windows)
• software frozen in “onedir” mode
• other platforms (GNU/Linux, OS X, BSD, etc.)