How severe is CVE-2021-21657?

CVE-2021-21657 has a CVSS score of 8.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-21657?

CVE-2021-21657 affects the following packages: org.jenkins-ci.plugins:fstrigger (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-21657?

Update org.jenkins-ci.plugins:fstrigger to 0.41 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21657 is resolved across your whole dependency graph.

How do I detect CVE-2021-21657 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.jenkins-ci.plugins:fstrigger, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-21657 if there is no patch (or I can't update yet)?

Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Is CVE-2021-21657 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-21657 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-21657?

CVE-2021-21657 has an EPSS (Exploit Prediction Scoring System) score of 1.6%, placing it in the 76th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2021-21657 published, and has it been updated?

CVE-2021-21657 was published on May 25, 2021 and was last updated on October 24, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

HIGH severity

CVE-2021-21657 — fstrigger

HIGH

CVE-2021-21657 is a high-severity (CVSS 8.8) vulnerability in org.jenkins-ci.plugins:fstrigger. A fix is available for org.jenkins-ci.plugins:fstrigger — see the affected versions and patch details below.

XXE vulnerability in Jenkins Filesystem Trigger Plugin

Also known asGHSA-cphv-7cxw-5hcc

Published

May 25, 2021

Updated

Oct 24, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs76th percentile — riskier than 76% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

☕org.jenkins-ci.plugins:fstrigger

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Jenkins Filesystem Trigger Plugin 0.40 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks.

This allows attackers with Job/Configure permission or otherwise able to control the contents of an XML file being polled for changes to have Jenkins parse a crafted XML document that uses external entities for extraction of secrets from the polling Jenkins controller or agent, server-side request forgery, or denial-of-service attacks.

Jenkins Filesystem Trigger Plugin 0.41 disables external entity resolution for its XML parser.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.jenkins-ci.plugins:fstrigger`	all versions	0.41`org.jenkins-ci.plugins:fstrigger:0.41`

Affected Products

1 product · 1 configurations

Application

filesystem triggerjenkins

≤ 0.40

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.jenkins-ci.plugins:fstrigger, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.jenkins-ci.plugins:fstrigger to 0.41 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21657 is resolved across your whole dependency graph.
Workarounds
Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Frequently Asked Questions

Jenkins Filesystem Trigger Plugin 0.40 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks. This allows attackers with Job/Configure permission or otherwise able to control the contents of an XML file being polled for changes to have Jenkins parse a crafted XML document that uses external entities for extraction of secrets from the polling Jenkins controller or agent, server-side request forgery, or denial-of-service attacks. Jenkins Filesystem Trigger Plugin 0.41 disables external entity resolution for its XML parser.

O3 Security · Impact-Aware SCA

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