What is CVE-2021-21684?

CVE-2021-21684 is a medium-severity vulnerability in Jenkins Git, classified under Improper Encoding or Escaping of Output. CVSS score: 6.1/10. Published 2021-10-06.

How severe is CVE-2021-21684?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Vulnerability in Jenkins Git

CVE-2021-21684

Jenkins Git Plugin 4.8.2 and earlier does not escape the Git SHA-1 checksum parameters provided to commit notifications when displaying them in a build cause, resulting in a stored cross-site scripting (XSS) vulnerability.

Published 2021-10-06 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.012 (67.9th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 68th percentile — 67.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.012 · newest: 0.012 · change: 0.000

Affected products

Jenkins Git
Jenkins Project Git Plugin — versions unspecified, 4.7.1.1, 4.3.1

Weakness classification (CWE)

CWE-116 — Improper Encoding or Escaping of Output

References

www.jenkins.io/security/advisory/2021-10-06/ (Vendor Advisory)
www.openwall.com/lists/oss-security/2021/10/06/1 (mailing-list, Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2021-21684?: CVE-2021-21684 is a medium-severity vulnerability in Jenkins Git, classified under Improper Encoding or Escaping of Output. CVSS score: 6.1/10. Published 2021-10-06.
How severe is CVE-2021-21684?: Medium severity. CVSS v3 base score is 6.1 out of 10.