CVE-2021-31200Network attack vector

Remote code execution via unsafe YAML deserialization

Published May 11, 2021 · Updated Aug 3, 2024

Unsafe YAML deserialization in Microsoft NNI before 3.0 allows remote authenticated users to execute arbitrary code through crafted YAML. The get_yml_content function passes the file to yaml.load with yaml.Loader, allowing Python object construction instead of restricting YAML types. Exploitation requires high-privileged network access and runs code with the privileges of the NNI process.

CVSS severity7.2
High
EPSS probability2.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unsafe YAML deserialization in Microsoft NNI before 3.0 allows remote authenticated users to execute arbitrary code through crafted YAML. The get_yml_content function passes the file to yaml.load with yaml.Loader, allowing Python object construction instead of restricting YAML types. Exploitation requires high-privileged network access and runs code with the privileges of the NNI process.

The record

CVE
CVE-2021-31200
Published
May 11, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
Unavailable
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. May 11, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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 privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.2Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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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