CVE-2021-21657Network attack vector

Secret extraction and SSRF via external entities

Published May 25, 2021 · Updated Aug 3, 2024

XXE in Jenkins Project Filesystem Trigger Plugin 0.40 and earlier allows attackers to read secrets through crafted polled XML files. The plugin's polling XML parser resolves external entities from attacker-controlled documents instead of disabling that feature. Job/Configure permission or control over a polled XML file is required; exploitation extracts controller or agent secrets, makes server-side requests, or interrupts service.

CVSS severity8.8
High
EPSS probability1.60%
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

XXE in Jenkins Project Filesystem Trigger Plugin 0.40 and earlier allows attackers to read secrets through crafted polled XML files. The plugin's polling XML parser resolves external entities from attacker-controlled documents instead of disabling that feature. Job/Configure permission or control over a polled XML file is required; exploitation extracts controller or agent secrets, makes server-side requests, or interrupts service.

The record

CVE
CVE-2021-21657
Published
May 25, 2021
Updated
Aug 3, 2024
Vendor
Jenkins Project
Product
Filesystem Trigger Plugin
Classifications
CWE-611, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 25, 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 <=0.40

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Jenkins Project · Filesystem Trigger Pluginversion=unspecified <=0.40

Published CVSS scores

8.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-611Improper Restriction of XML External Entity Reference
T1190Exploit Public-Facing Application

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