CVE-2021-39887 Cross-site scripting in GitLab

High 7.3 Published 5 Oct 2021 Updated 4 Aug 2024

An attacker can execute arbitrary JavaScript on victims via stored XSS in GitLab Flavored Markdown, potentially leading to account takeover.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2021-39887?

CVE-2021-39887 is a high-severity cross-site scripting vulnerability in Gitlab Gitlab, published on 5 Oct 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official 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.

Weakness: CWE-79

Which versions are affected by CVE-2021-39887?

1 open source package ship an affected version, including gitlab. It affects 1 product.

Package	Affected	Fixed in
`gitlab` Bitnami	From `8.4.0`	`14.1.7, 14.2.5, 14.3.1`

Products include Gitlab Gitlab.

How do I fix CVE-2021-39887?

Upgrade gitlab to a fixed version for your release line: 14.1.7, 14.2.5 or 14.3.1.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2021-39887 being exploited?

There is no known exploitation of CVE-2021-39887 in the wild and no public exploit code.

All Gitlab Gitlab vulnerabilities

Sources

Also known as BIT-gitlab-2021-39887, GHSA-8j2x-wq4x-63v8, UBUNTU-CVE-2021-39887.