Cyber Posture

CVE-2026-21531

Critical

Published: 10 February 2026

Published
10 February 2026
Modified
12 February 2026
KEV Added
Patch
CVSS Score 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0048 65.2th percentile
Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Description

Deserialization of untrusted data in Azure SDK allows an unauthorized attacker to execute code over a network.

Mitigating Controls (NIST 800-53 r5)AI

prevent

Directly remediates the deserialization flaw in Azure SDK through timely patching as recommended in Microsoft's update guide.

prevent

Validates untrusted network inputs prior to deserialization by the Azure SDK to block malicious payloads.

prevent

Implements memory protections like ASLR and DEP to mitigate remote code execution from deserialization exploits.

Security SummaryAI

CVE-2026-21531 is a deserialization of untrusted data vulnerability (CWE-502) in the Azure SDK. Published on 2026-02-10T18:16:35.580, it carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating critical severity due to its potential for severe impact across confidentiality, integrity, and availability.

The vulnerability enables an unauthorized attacker to execute code over a network. Exploitation requires network access with low attack complexity, no privileges, and no user interaction, allowing remote code execution against affected Azure SDK implementations.

Microsoft's Security Response Center provides an update guide for this vulnerability at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21531, which security practitioners should consult for mitigation and patching details.

Details

CWE(s)

Affected Products

microsoft
azure conversation authoring client library
1.0.0

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
Why these techniques?

Deserialization vulnerability (CWE-502) in Azure SDK enables remote code execution over the network with no privileges or user interaction (AV:N/AC:L/PR:N/UI:N), directly facilitating exploitation of public-facing applications.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

References