CVE-2021-21611Network attack vector

Stored script execution via unescaped item metadata

Published Jan 13, 2021 · Updated Aug 3, 2024

Stored XSS in the New Item page in Jenkins 2.274 and earlier and LTS 2.263.1 and earlier allows attackers to execute script in a viewer's browser. The New Item page inserts item-type display names and IDs supplied by extension metadata into HTML without escaping them. Exploitation requires an installed item type that lets an attacker control that metadata and a user to open the page; the vendor knew of no such plugin in its update center.

CVSS severity5.4
Medium
EPSS probability1.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in the New Item page in Jenkins 2.274 and earlier and LTS 2.263.1 and earlier allows attackers to execute script in a viewer's browser. The New Item page inserts item-type display names and IDs supplied by extension metadata into HTML without escaping them. Exploitation requires an installed item type that lets an attacker control that metadata and a user to open the page; the vendor knew of no such plugin in its update center.

The record

CVE
CVE-2021-21611
Published
Jan 13, 2021
Updated
Aug 3, 2024
Vendor
Jenkins Project
Product
Jenkins
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 13, 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 <=2.274
  2. Affected versionversion=unspecified <=LTS 2.263.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Jenkins Project · Jenkinsversion=unspecified <=2.274; version=unspecified <=LTS 2.263.1

Published CVSS scores

3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/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-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

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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