What is CVE-2021-21686?

CVE-2021-21686 is a high-severity vulnerability in Jenkins, classified under Improper Link Resolution Before File Access. CVSS score: 8.1/10. Published 2021-11-04.

How severe is CVE-2021-21686?

High severity. CVSS v3 base score is 8.1 out of 10.

Is CVE-2021-21686 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Jenkins

CVE-2021-21686

File path filters in the agent-to-controller security subsystem of Jenkins 2.318 and earlier, LTS 2.303.2 and earlier do not canonicalize paths, allowing operations to follow symbolic links to outside allowed directories.

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

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.020 (79.7th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 80th percentile — 79.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.020 · newest: 0.020 · change: 0.000

Affected products

Jenkins
Jenkins Project — versions unspecified

Weakness classification (CWE)

CWE-59 — Improper Link Resolution Before File Access

Public proof-of-concept exploits

ARPSyndicate/cvemon

References

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

Frequently asked questions

What is CVE-2021-21686?: CVE-2021-21686 is a high-severity vulnerability in Jenkins, classified under Improper Link Resolution Before File Access. CVSS score: 8.1/10. Published 2021-11-04.
How severe is CVE-2021-21686?: High severity. CVSS v3 base score is 8.1 out of 10.
Is CVE-2021-21686 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.