CVE-2021-21639Network attack vector

Node replacement via unchecked object type

Published Apr 7, 2021 · Updated Aug 3, 2024

Improper input validation in Jenkins 2.286 and earlier and LTS 2.277.1 and earlier allows remote authenticated users to replace nodes via the config.xml REST API. The node configuration loader accepts submitted XML without validating that the created object matches the expected node type, allowing a Computer/Configure user to substitute a different node implementation. Exploitation requires authenticated access with Computer/Configure permission and changes node integrity rather than directly exposing data or executing code.

CVSS severity4.3
Medium
EPSS probability2.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Jenkins 2.286 and earlier and LTS 2.277.1 and earlier allows remote authenticated users to replace nodes via the config.xml REST API. The node configuration loader accepts submitted XML without validating that the created object matches the expected node type, allowing a Computer/Configure user to substitute a different node implementation. Exploitation requires authenticated access with Computer/Configure permission and changes node integrity rather than directly exposing data or executing code.

The record

CVE
CVE-2021-21639
Published
Apr 7, 2021
Updated
Aug 3, 2024
Vendor
Jenkins Project
Product
Jenkins
Classifications
CWE-20
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 7, 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 <=2.286
  2. Affected versionversion=unspecified <=LTS 2.277.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Jenkins Project · Jenkinsversion=unspecified <=2.286; version=unspecified <=LTS 2.277.1

Published CVSS scores

4.3NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
4.0NVDAV:N/AC:L/Au:S/C:N/I:P/A:N

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation

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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