CVE-2019-16784

In PyInstaller before version 3.6, only on Windows, a local privilege escalation vulnerability is present in this particular case: If a software using PyInstaller in "onefile" mode is launched by a privileged user (at least more than the current one) which have his "TempPath" resolving to a world writable directory. This is the case for example if the software is launched as a service or as a scheduled task using a system account (TempPath will be C:\Windows\Temp). In order to be exploitable the software has to be (re)started after the attacker launch the exploit program, so for a service launched at startup, a service restart is needed (e.g. after a crash or an upgrade).

In PyInstaller before version 3.6, only on Windows, a local privilege escalation vulnerability is present in this particular case: If a software using PyInstaller in "onefile" mode is launched by a privileged user (at least more than the current one) which have his "TempPath" resolving to a world writable directory. This is the case for example if the software is launched as a service or as a scheduled task using a system account (TempPath will be C:\Windows\Temp). In order to be exploitable the software has to be (re)started after the attacker launch the exploit program, so for a service launched at startup, a service restart is needed (e.g. after a crash or an upgrade).

In PyInstaller before version 3.6, only on Windows, a local privilege escalation vulnerability is present in this particular case: If a software using PyInstaller in "onefile" mode is launched by a privileged user (at least more than the current one) which have his "TempPath" resolving to a world writable directory. This is the case for example if the software is launched as a service or as a scheduled task using a system account (TempPath will be C:\Windows\Temp). In order to be exploitable the software has to be (re)started after the attacker launch the exploit program, so for a service launched at startup, a service restart is needed (e.g. after a crash or an upgrade).

### Impact 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 "one*dir*" mode - other platforms (GNU/Linux, OS X, BSD, etc.) ### Patches The problem is patched in commits 42a67148b3bdf9211fda8499fdc5b63acdd7e6cc (fixed code) and be948cf0954707671aa499da17b10c86b6fa5e5c (recompiled bootloaders). Users should upgrade to PyInstaller version 3.6 and rebuild their software. ### Workarounds There is no known workaround. Users using PyInstaller to freeze their Windows software using "onefile" mode should upgrade PyInstaller and rebuild their software. ### Credits This vulnerability was discovered and reported by Farid AYOUJIL (@faridtsl), David HA, Florent LE NIGER and Yann GASCUEL (@lnv42) from Alter Solutions (@AlterSolutions) and fixed in collaboration with Hartmut Goebel (@htgoebel, maintainer of PyInstaller). ### Funding Development PyInstaller is in urgent need of funding to make future security fixes happen, see <https://github.com/pyinstaller/pyinstaller/issues/4404> for details.

En PyInstaller versiones anteriores a 3.6, solo sobre Windows, se presenta una vulnerabilidad de escalada de privilegios local en este caso particular: si un software que usa PyInstaller en modo "onefile" es activado por un usuario privilegiado (al menos más que el actual) que tiene su "TempPath" resolviendo en un directorio de tipo world writable. Este es el caso, por ejemplo, si el software es iniciado como un servicio o como una tarea programada utilizando una cuenta system (TempPath será C:\Windows\Temp). A fin de ser explotable, el software tiene que ser reiniciado después de que el atacante active el programa de explotación, por lo que para un servicio activado en el inicio, es necesario reiniciar el servicio (por ejemplo, después de un bloqueo o una actualización).