CVE-2026-21226

Azure Core Meltdown: When Deserialization Goes Wrong in Python

Alon Barad
Alon Barad
Software Engineer

Jan 14, 2026·5 min read·33 visits

Executive Summary (TL;DR)

The foundation of Azure's Python SDKs, `azure-core`, contained a deserialization flaw (CWE-502). By feeding a crafted object to a vulnerable application, an attacker with low privileges could execute arbitrary code. Microsoft patched this in version 1.38.0.

A critical insecure deserialization vulnerability in the Microsoft Azure Core shared client library for Python allows authenticated attackers to achieve Remote Code Execution (RCE).

Official Patches

MicrosoftAzure Core Changelog noting the fix

Technical Appendix

CVSS Score
7.5/ 10
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected Systems

Python applications using Azure SDKsAzure CLI extensions (Python-based)Data pipelines using Azure Data Factory custom Python activitiesWeb apps using Azure Identity for Python

Affected Versions Detail

Product
Affected Versions
Fixed Version
azure-core
Microsoft
>= 1.1.0, < 1.38.01.38.0
AttributeDetail
CWE IDCWE-502
CVSS v3.17.5 (High)
Attack VectorNetwork
Privileges RequiredLow
Attack ComplexityHigh
ImpactRemote Code Execution (RCE)

MITRE ATT&CK Mapping

T1587.004Develop Capabilities: Exploits
Resource Development
T1059.006Command and Scripting Interpreter: Python
Execution
T1203Exploitation for Client Execution
Execution
CWE-502
Deserialization of Untrusted Data

Deserialization of Untrusted Data

Vulnerability Timeline

Vulnerability Published by Microsoft
2026-01-13
Patch 1.38.0 Released
2026-01-13
GHSA-jm66-cg57-jjv5 Published
2026-01-13