Summary
Local Privilege Escalation in PyInstaller
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.
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 "onedir" mode
- other platforms (GNU/Linux, OS X, BSD, etc.)
CVE-2019-16784 has a CVSS score of 7.0 (High). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.6); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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See it in your environmentNew to Kodem? Get a demo →Remediation advice
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.
Frequently Asked Questions
- What is CVE-2019-16784? CVE-2019-16784 is a high-severity security vulnerability in PyInstaller (pip), affecting versions < 3.6. It is fixed in 3.6.
- How severe is CVE-2019-16784? CVE-2019-16784 has a CVSS score of 7.0 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of PyInstaller are affected by CVE-2019-16784? PyInstaller (pip) versions < 3.6 is affected.
- Is there a fix for CVE-2019-16784? Yes. CVE-2019-16784 is fixed in 3.6. Upgrade to this version or later.
- Is CVE-2019-16784 exploitable, and should I be worried? Whether CVE-2019-16784 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2019-16784 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2019-16784? Upgrade
PyInstallerto 3.6 or later.