CVE-2021-21628Network attack vector

Authenticated stored XSS via unescaped parameter metadata

Published Mar 30, 2021 · Updated Aug 3, 2024

Stored cross-site scripting in Jenkins Build With Parameters Plugin 1.5 and earlier allows remote authenticated users to execute script via crafted parameter names. The BuildWithParametersAction index view inserts parameter names and descriptions without escaping, allowing attacker-controlled markup to persist in job configuration and execute when rendered by a user. Exploitation requires Job/Configure permission and a victim browser viewing the affected job; impact is script execution in that browser's Jenkins security context.

CVSS severity5.4
Medium
EPSS probability81.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Stored cross-site scripting in Jenkins Build With Parameters Plugin 1.5 and earlier allows remote authenticated users to execute script via crafted parameter names. The BuildWithParametersAction index view inserts parameter names and descriptions without escaping, allowing attacker-controlled markup to persist in job configuration and execute when rendered by a user. Exploitation requires Job/Configure permission and a victim browser viewing the affected job; impact is script execution in that browser's Jenkins security context.

The record

CVE
CVE-2021-21628
Published
Mar 30, 2021
Updated
Aug 3, 2024
Vendor
Jenkins Project
Product
Build With Parameters Plugin
Classifications
CWE-79, T1189
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 30, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=unspecified <=1.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Jenkins Project · Build With Parameters Pluginversion=unspecified <=1.5

Published CVSS scores

5.4NVDCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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')
T1189Drive-by Compromise

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo