CVE-2019-16784: Local Privilege Escalation present only on the Windows version of PyInstaller
First published: Tue Jan 14 2020(Updated: )
### 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.
Credit: security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| pip/PyInstaller | <3.6 | 3.6 |
| All of | ||
| App Installer | <3.6 | |
| Microsoft Windows Operating System | ||
| App Installer | <3.6 | |
| Microsoft Windows Operating System |
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Reference Links
- https://github.com/pyinstaller/pyinstaller/security/advisories/GHSA-7fcj-pq9j-wh2r
- https://github.com/pyinstaller/pyinstaller/commit/42a67148b3bdf9211fda8499fdc5b63acdd7e6cc
- https://github.com/pyinstaller/pyinstaller/commit/be948cf0954707671aa499da17b10c86b6fa5e5c
- https://nvd.nist.gov/vuln/detail/CVE-2019-16784
- https://github.com/pypa/advisory-database/tree/main/vulns/pyinstaller/PYSEC-2020-175.yaml
- https://github.com/advisories/GHSA-7fcj-pq9j-wh2r (Advisory)
Frequently Asked Questions
What is the severity of CVE-2019-16784?
The severity of CVE-2019-16784 is classified as a local privilege escalation vulnerability.
How do I fix CVE-2019-16784?
To fix CVE-2019-16784, upgrade PyInstaller to version 3.6 or higher.
Who is affected by CVE-2019-16784?
CVE-2019-16784 affects all Windows software that has been frozen by PyInstaller in 'onefile' mode.
What can be exploited in CVE-2019-16784?
CVE-2019-16784 can be exploited by a privileged user who launches the vulnerable software.
Is CVE-2019-16784 present in all versions of PyInstaller?
No, CVE-2019-16784 is present only in PyInstaller versions below 3.6.
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