What is CVE-2021-39878?

CVE-2021-39878 is a medium-severity vulnerability in GitLab, classified under Cross-site Scripting. CVSS score: 5.8/10. Published 2021-10-05.

How severe is CVE-2021-39878?

Medium severity. CVSS v3 base score is 5.8 out of 10.

XSS in GitLab

CVE-2021-39878

A stored Reflected Cross-Site Scripting vulnerability in the Jira integration in GitLab version 13.0 up to 14.3.1 allowed an attacker to execute arbitrary javascript code.

Vulnerability class: XSS (Cross-Site Scripting)

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

CVSS v3 metric

CVSS v3 base score 5.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.008 (55.1th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 55th percentile — 55.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

GitLab — versions >=13.0, <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/334043 (Broken Link)
hackerone.com/reports/1194254 (Permissions Required)
gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39878.json (Vendor Advisory)

Frequently asked questions

What is CVE-2021-39878?: CVE-2021-39878 is a medium-severity vulnerability in GitLab, classified under Cross-site Scripting. CVSS score: 5.8/10. Published 2021-10-05.
How severe is CVE-2021-39878?: Medium severity. CVSS v3 base score is 5.8 out of 10.