CVE-2025-12734 Improper Encoding or Escaping of Output in GitLab

Low 3.5 Published 11 Dec 2025 Updated 16 Dec 2025

Authenticated users can inject malicious HTML into merge request titles, potentially executing scripts in other users' browsers.

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-2025-12734?

CVE-2025-12734 is a low-severity cross-site scripting vulnerability in Gitlab Gitlab, published on 11 Dec 2025. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official description

GitLab has remediated an issue in GitLab CE/EE affecting all versions from 15.6 before 18.4.6, 18.5 before 18.5.4, and 18.6 before 18.6.2 that could have allowed an authenticated user to, under certain conditions, render content in dialogs to other users by injecting malicious HTML content into merge request titles.

Weakness: CWE-116

Which versions are affected by CVE-2025-12734?

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

Package	Affected	Fixed in
`gitlab` Bitnami	From `15.6.0`	`18.4.6, 18.5.4, 18.6.2`

Products include Gitlab Gitlab.

How do I fix CVE-2025-12734?

Upgrade gitlab to a fixed version for your release line: 18.4.6, 18.5.4 or 18.6.2.

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-2025-12734 being exploited?

There is no known exploitation of CVE-2025-12734 in the wild and no public exploit code.

All Gitlab Gitlab vulnerabilities

Sources

Also known as BIT-gitlab-2025-12734, GHSA-cpx5-2q84-prc5, UBUNTU-CVE-2025-12734.