CVE-2021-24040Public exploit

Code execution via unsafe YAML configuration loading

Published Sep 10, 2021 · Updated Aug 3, 2024

Unsafe YAML deserialization in Meta Platforms, Inc. ParlAI before 1.1.0 allows local users to execute code through a crafted configuration file. parse_configuration_file used yaml.FullLoader, while ModelChatBlueprint._get_shared_models called yaml.load without a safe loader, permitting Python object construction from YAML tags. An attacker must be able to replace a local chat-service or model-options YAML file that a ParlAI process later loads, yielding code execution with that process's privileges.

CVSS severity9.8
Critical
EPSS probability17.35%
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 Meta Platforms, Inc. ParlAI before 1.1.0 allows local users to execute code through a crafted configuration file. parse_configuration_file used yaml.FullLoader, while ModelChatBlueprint._get_shared_models called yaml.load without a safe loader, permitting Python object construction from YAML tags. An attacker must be able to replace a local chat-service or model-options YAML file that a ParlAI process later loads, yielding code execution with that process's privileges.

The record

CVE
CVE-2021-24040
Published
Sep 10, 2021
Updated
Aug 3, 2024
Vendor
Meta Platforms, Inc.
Product
ParlAI
Classifications
CWE-502, T1059.006
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 10, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <1.1.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

Meta Platforms, Inc. · ParlAIversion=unspecified <1.1.0

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
T1059.006Python

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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