What is CVE-2021-21687?

CVE-2021-21687 is a critical-severity vulnerability in Jenkins, classified under Missing Authorization. CVSS score: 9.1/10. Published 2021-11-04.

How severe is CVE-2021-21687?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Auth bypass in Jenkins

CVE-2021-21687

Jenkins 2.318 and earlier, LTS 2.303.2 and earlier does not check agent-to-controller access to create symbolic links when unarchiving a symbolic link in FilePath#untar.

Vulnerability class: Broken Access Control

Published 2021-11-04 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.014 (71.1th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 71st percentile — 71.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.014 · newest: 0.014 · change: 0.000

Affected products

Jenkins
Jenkins Project — versions unspecified

Weakness classification (CWE)

CWE-862 — Missing Authorization

References

www.jenkins.io/security/advisory/2021-11-04/ (Vendor Advisory)

Frequently asked questions

What is CVE-2021-21687?: CVE-2021-21687 is a critical-severity vulnerability in Jenkins, classified under Missing Authorization. CVSS score: 9.1/10. Published 2021-11-04.
How severe is CVE-2021-21687?: Critical severity. CVSS v3 base score is 9.1 out of 10.