What is CVE-2021-39887?

CVE-2021-39887 is a high-severity vulnerability in GitLab, classified under Cross-site Scripting. CVSS score: 7.3/10. Published 2021-10-05.

How severe is CVE-2021-39887?

High severity. CVSS v3 base score is 7.3 out of 10.

XSS in GitLab

CVE-2021-39887

A stored Cross-Site Scripting vulnerability in the GitLab Flavored Markdown in GitLab CE/EE version 8.4 and above allowed an attacker to execute arbitrary JavaScript code on the victim's behalf.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-10-05 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.3 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.009 (57.0th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 57th percentile — 57.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

GitLab — versions >=8.4, <14.1.7, >=14.2, <14.2.5, >=14.3, <14.3.1

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

gitlab.com/gitlab-org/gitlab/-/issues/332903 (Broken Link)
hackerone.com/reports/1218174 (Permissions Required, Third Party Advisory)
gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39887.json (Vendor Advisory)

Frequently asked questions

What is CVE-2021-39887?: CVE-2021-39887 is a high-severity vulnerability in GitLab, classified under Cross-site Scripting. CVSS score: 7.3/10. Published 2021-10-05.
How severe is CVE-2021-39887?: High severity. CVSS v3 base score is 7.3 out of 10.