CVE-2021-39887

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-10-05 · updated 2026-06-17
Weakness: CWE-79

Description

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.

Affected products

GitLab: from 8.4.0 before 14.1.7; from 14.2 before 14.2.5; from 14.3 before 14.3.1 — fixed in 14.1.7, 14.2.5, 14.3.1

How to fix

Upgrade to a fixed version: GitLab 14.1.7, 14.2.5, 14.3.1. Check the vendor advisory for mitigations.

References

https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39887.json
https://gitlab.com/gitlab-org/gitlab/-/issues/332903
https://hackerone.com/reports/1218174
https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39887.json
https://gitlab.com/gitlab-org/gitlab/-/issues/332903
https://hackerone.com/reports/1218174

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