CVE-2025-59042 — pyinstaller
Fix: pyinstaller/pyinstaller@f5adf29CVE-2025-59042 is a Code Injection vulnerability in pyinstaller. A fix is available for pyinstaller — see the affected versions and patch details below.
PyInstaller has local privilege escalation vulnerability
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-59042.
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.
Real-World Exposure
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 | 6.0.0pip install --upgrade 'pyinstaller==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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-59042 can be triaged on real exposure rather than presence alone.
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 Security finds CVE-2025-59042 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.