CVE-2021-40146Public exploitNetwork attack vector

Remote code execution via unsafe YAML deserialization

Published Sep 11, 2021 · Updated Aug 4, 2024

Unsafe YAML deserialization in Apache Any23 before 2.5 allows remote attackers to execute arbitrary code through crafted YAML input. YAMLExtractor passes untrusted documents to SnakeYAML loadAll(), which instantiates attacker-specified Java classes without a SafeConstructor allowlist. An unauthenticated reachable REST service can fetch the YAML and a gadget JAR, granting the attacker the service account's privileges.

CVSS severity9.8
Critical
EPSS probability5.68%
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 Apache Any23 before 2.5 allows remote attackers to execute arbitrary code through crafted YAML input. YAMLExtractor passes untrusted documents to SnakeYAML loadAll(), which instantiates attacker-specified Java classes without a SafeConstructor allowlist. An unauthenticated reachable REST service can fetch the YAML and a gadget JAR, granting the attacker the service account's privileges.

The record

CVE
CVE-2021-40146
Published
Sep 11, 2021
Updated
Aug 4, 2024
Vendor
The Apache Software Foundation
Product
Apache Any23
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 11, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=Apache Any23 <2.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Any23version=Apache Any23 <2.5

Published CVSS scores

10.0NIST NVDAV:N/AC:L/Au:N/C:C/I:C/A:C
9.8NIST NVDCVSS: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.

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1190Exploit Public-Facing Application

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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