CVE-2025-59042
PyInstaller has local privilege escalation vulnerability
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
pyinstallerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
PyInstaller bundles a Python application and all its dependencies into a single package. Due to a special entry being appended to sys.path during the bootstrap process of a PyInstaller-frozen application, and due to the bootstrap script attempting to load an optional module for bytecode decryption while this entry is still present in sys.path, an application built with PyInstaller < 6.0.0 may be tricked by an unprivileged attacker into executing arbitrary python code when all of the following conditions are met. First, the application is built with PyInstaller < 6.0.0; both onedir and onefile mode are affected. Second, the optional bytecode encryption code feature was not enabled during the application build. Third, the attacker can create files/directories in the same directory where the executable is located. Fourth, the filesystem supports creation of files/directories that contain ? in their name (i.e., non-Windows systems). Fifth, the attacker is able to determine the offset at which the PYZ archive is embedded in the executable. The attacker can create a directory (or a zip archive) next to the executable, with the name that matches the format used by PyInstaller's bootloader to transmit information about the location of PYZ archive to the bootstrap script. If this directory (or zip archive) contains a python module whose name matches the name used by the optional bytecode encryption feature, this module will be loaded and executed by the bootstrap script (in the absence of the real, built-in module that is available when the bytecode-encryption feature is enabled). This results in arbitrary code execution that requires no modification of the executable itself. If the executable is running with elevated privileges (for example, due to having the setuid bit set), the code in the injected module is also executed with the said elevated privileges, resulting in a local privilege escalation. PyInstaller 6.0.0 (f5adf291c8b832d5aff7632844f7e3ddf7ad4923) removed support for bytecode encryption; this effectively removes the described attack vector, due to the bootstrap script not attempting to load the optional module for bytecode-decryption anymore. PyInstaller 6.10.0 (cfd60b510f95f92cb81fc42735c399bb781a4739) reworked the bootstrap process to avoid (ab)using sys.path for transmitting location of the PYZ archive, which further eliminates the possibility of described injection procedure. If upgrading PyInstaller is not feasible, this issue can be worked around by ensuring proper permissions on directories containing security-sensitive executables (i.e., executables with setuid bit set) should mitigate the issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pyinstaller | all versions | 6.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyinstaller. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update pyinstaller to 6.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-59042 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2025-59042 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2025-59042. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-59042 in your dependencies?
O3 detects CVE-2025-59042 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.