CVE-2026-21531Network attack vector

Unauthenticated code execution via unsafe token deserialization

Published Feb 10, 2026 · Updated Feb 10, 2026

Deserialization in Microsoft Azure AI Language Conversations Authoring before 1.0.0b4 allows remote attackers to execute arbitrary code. The continuation-token restoration path deserializes a caller-supplied token as a Python object without authenticity or type validation. Exploitation requires an application to process an attacker-controlled continuation token; no authentication or user interaction is required.

CVSS severity9.8
Critical
EPSS probability2.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Deserialization in Microsoft Azure AI Language Conversations Authoring before 1.0.0b4 allows remote attackers to execute arbitrary code. The continuation-token restoration path deserializes a caller-supplied token as a Python object without authenticity or type validation. Exploitation requires an application to process an attacker-controlled continuation token; no authentication or user interaction is required.

The record

CVE
CVE-2026-21531
Published
Feb 10, 2026
Updated
Feb 10, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-502, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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