How severe is CVE-2021-21620?

CVE-2021-21620 has a CVSS score of 4.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-21620?

CVE-2021-21620 affects the following packages: org.jenkins-ci.plugins:claim (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-21620?

Update org.jenkins-ci.plugins:claim to 2.18.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21620 is resolved across your whole dependency graph.

How do I detect CVE-2021-21620 in my Maven dependencies?

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

How do I mitigate CVE-2021-21620 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2021-21620 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-21620 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-2021-21620?

CVE-2021-21620 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.

What type of vulnerability is CVE-2021-21620?

CVE-2021-21620 is classified as Cross-Site Request Forgery (CSRF) (CWE-352). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-21620 published, and has it been updated?

CVE-2021-21620 was published on February 24, 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

MEDIUM severity

CVE-2021-21620 — claim

MEDIUM

CVE-2021-21620 is a medium-severity (CVSS 4.3) Cross-Site Request Forgery (CSRF) vulnerability in org.jenkins-ci.plugins:claim. A fix is available for org.jenkins-ci.plugins:claim — see the affected versions and patch details below.

Cross-Site Request Forgery in the Jenkins Claim plugin

Also known asGHSA-4ffq-6g62-j4v4

Published

Feb 24, 2021

Updated

Oct 24, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 3, 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:claim

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 Claim Plugin 2.18.1 and earlier does not require POST requests for the form submission endpoint assigning claims, resulting in a cross-site request forgery (CSRF) vulnerability.

This vulnerability allows attackers to change claims.

Jenkins Claim Plugin 2.18.2 requires POST requests for the affected HTTP endpoint.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.jenkins-ci.plugins:claim`	all versions	2.18.2`org.jenkins-ci.plugins:claim:2.18.2`

Affected Products

1 product · 1 configurations

Application

claimjenkins

≤ 2.18.1

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:claim, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.jenkins-ci.plugins:claim to 2.18.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21620 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Jenkins Claim Plugin 2.18.1 and earlier does not require POST requests for the form submission endpoint assigning claims, resulting in a cross-site request forgery (CSRF) vulnerability. This vulnerability allows attackers to change claims. Jenkins Claim Plugin 2.18.2 requires POST requests for the affected HTTP endpoint.

O3 Security · Impact-Aware SCA

Is CVE-2021-21620 in your dependencies?

Find it across Maven, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

4.3/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

CWE Classification

CWE-352Cross-Site Request Forgery (CSRF)

Weaponization

No Nuclei template, Metasploit module or public proof-of-concept found.

Timeline

Disclosed

Feb 24, 2021

Last updated

Oct 24, 2026

Identifiers

CVE-2021-21620

GHSA-4ffq-6g62-j4v4

References

Advisoryjenkins.io · 2021 02 24 Advisorynvd.nist.gov · CVE 2021 21620 Webjenkins.io · 2021 02 24 Packagegithub.com · claim plugin

Related vulnerabilities

Also affects claim

This CVE is medium severity, in line with the other 1 CVE affecting claim.

CVE-2021-21619

Same weakness: CWE-352

This CVE is medium severity; 6 of 7 other CVEs with CWE-352 are rated as high or higher (top: high).

CVE-2026-126067CVE-2026-109481CVE-2026-96629CVE-2026-118266CVE-2026-113796CVE-2026-84312CVE-2026-62322Browse all CWE-352

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 24, 2026

CVE-2021-21620 — claim

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2021-21620 in your dependencies?