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CVE-2024-21338 affects the Azure Core shared client library for Python. This library provides common functionality for Azure SDKs. The vulnerability stems from insecure deserialization of untrusted data using Python’s pickle module. When the library deserializes data from network sources without validation, it can execute arbitrary code. An authorized attacker can send crafted serialized data to endpoints using the library. The deserialization process in components like Deserializer.deserialize() calls pickle.loads() on untrusted input. Pickle allows execution of code during deserialization, so malicious payloads can run commands. The attack vector is over a network, requiring authorization but enabling remote code execution. Vulnerable functions include those handling serialized objects in HTTP responses or messages. The library fails to sanitize input before deserialization, trusting data from APIs or services. This can be exploited in Azure services relying on the core library for communication. The flaw allows attackers to compromise application integrity and confidentiality. It is particularly risky in multi-tenant environments due to data isolation issues. The vulnerability exists in versions before patches implemented safe deserialization. Mitigation involves using secure formats or validating input. The issue highlights the danger of pickle for untrusted data. Patches replace pickle with JSON or add validation checks. Exploitation leads to full system control, data theft, and service disruption. Network-facing applications using Azure Core are at direct risk. The vulnerability is rated high due to the potential for remote code execution.
Platform: Azure Core Python
Version: < 1.0.0
Vulnerability: Deserialization of Untrusted Data
Severity: High
Date: Jan 13 2026
Prediction: Patch by Jan 20 2026
What Undercode Say:
pip show azure-core pip install azure-core==1.0.0
import pickle
malicious_data = pickle.dumps(os.system('id'))
In vulnerable Azure Core code:
from azure.core.serialization import Deserializer
Deserializer.deserialize(malicious_data)
how Exploit:
Authorized attacker sends malicious pickle payload via network to Azure Core endpoint. Deserialization executes arbitrary code, like shell commands, compromising the system.
Protection from this CVE:
Upgrade to azure-core>=1.0.0. Use JSON serialization instead of pickle. Validate and sanitize all input data before deserialization.
Impact:
Remote code execution, data breach, system takeover, service disruption.
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Sources:
Reported By: github.com
Extra Source Hub:
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