CVE-2021-31681Public exploit

Code execution via unsafe YAML loading

Published Jul 31, 2023 · Updated Oct 22, 2024

Deserialization of untrusted data in Ultralytics YOLOv3 allows local users to execute arbitrary code by supplying a crafted YAML file. The train.py script loads training data, model configuration, and hyperparameter YAML with yaml.FullLoader, permitting Python object construction from attacker-controlled tags. Execution requires a user to run train.py with the malicious file, after which embedded commands run with that user's privileges.

CVSS severity7.8
High
EPSS probability0.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Deserialization of untrusted data in Ultralytics YOLOv3 allows local users to execute arbitrary code by supplying a crafted YAML file. The train.py script loads training data, model configuration, and hyperparameter YAML with yaml.FullLoader, permitting Python object construction from attacker-controlled tags. Execution requires a user to run train.py with the malicious file, after which embedded commands run with that user's privileges.

The record

CVE
CVE-2021-31681
Published
Jul 31, 2023
Updated
Oct 22, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-502, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 31, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 22, 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 vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
T1204.002User Execution: Malicious File

Public exploit references

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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