Deserialization of Untrusted Data Affecting jsonpickle package, versions [,4.0.2)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-PYTHON-JSONPICKLE-16755449
- published19 May 2026
- disclosed16 May 2026
- creditUnknown
Introduced: 16 May 2026
CVE-2021-47952 (opens in a new tab)How to fix?
Upgrade jsonpickle to version 4.0.2 or higher.
Overview
jsonpickle is a Python library for serializing any arbitrary object graph into JSON.
Affected versions of this package are vulnerable to Deserialization of Untrusted Data via the loadrepr() function in Unpickler. An attacker can execute arbitrary system commands by supplying malicious JSON payloads containing specially crafted py/repr objects.
Note:
According to the vendor: "The jsonpickle module is not secure. Only unpickle data you trust. It is possible to construct malicious pickle data which will execute arbitrary code during unpickling. Never unpickle data that could have come from an untrusted source, or that could have been tampered with."
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.