Critical RCE Vulnerability in Fickling Package: Missing Unsafe Imports
Summary
GHSA-5hwf-rc88-82xm: Fickling missing RCE-capable modules in UNSAFE_IMPORTS. Affects fickling versions < 0.1.9. Fixed in 0.1.9. How to fix ↓
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Background
Fickling is a Python library designed for safe serialization and deserialization of Python objects, particularly focusing on the security of the pickle format. It aims to prevent arbitrary code execution by validating imports during the unpickling process. However, it has been found to lack certain critical modules in its blocklist of unsafe imports, making it susceptible to remote code execution (RCE) attacks.
Vulnerability Detail
The vulnerability arises from Fickling's UNSAFE_IMPORTS blocklist, which fails to include three standard library modules: uuid, _osx_support, and _aix_support. These modules contain functions that can execute arbitrary commands through subprocess.Popen() or os.system() with attacker-controlled arguments. Consequently, a malicious pickle file that imports these modules can bypass Fickling's safety checks, leading to potential RCE. This issue affects all versions of Fickling up to and including 0.1.8, allowing attackers to craft pickle files that execute arbitrary system commands while being reported as 'LIKELY_SAFE' by Fickling.
How To Fix
Latest published version: 0.1.12 as of 23 Oct 2026
pip install --upgrade "fickling==0.1.12"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
0.1.9
This is the first release that contains the fix.
pip install --upgrade "fickling==0.1.9"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, avoid using Fickling for unpickling data from untrusted sources until the package is updated. Additionally, you can manually check the contents of pickle files before processing them to ensure they do not import the vulnerable modules.
Conclusion
The Fickling package has a critical vulnerability due to missing unsafe imports in its blocklist, allowing for potential remote code execution. Users are advised to update to the latest version to mitigate this risk and to exercise caution when handling untrusted pickle files.
See every vulnerability recorded for fickling →
FAQ
The CVSS score of this vulnerability is 8.9, indicating a high severity level.
All versions of Fickling up to and including 0.1.8 are affected by this vulnerability.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
If you cannot update Fickling immediately, avoid unpickling data from untrusted sources and manually inspect pickle files for unsafe imports.
The potential consequences include arbitrary command execution on the host system, which can lead to data breaches, system compromise, and other security incidents.
References
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