CVE-2021-39933 Denial of service in GitLab

Medium 4.3 Published 13 Dec 2021 Updated 4 Aug 2024

An attacker can cause a denial of service in GitLab by exploiting catastrophic backtracking in regular expressions used for user input handling.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2021-39933?

CVE-2021-39933 is a medium-severity denial of service vulnerability in Gitlab Gitlab, published on 13 Dec 2021. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

An issue has been discovered in GitLab CE/EE affecting all versions starting from 12.10 before 14.3.6, all versions starting from 14.4 before 14.4.4, all versions starting from 14.5 before 14.5.2. A regular expression used for handling user input (notes, comments, etc) was susceptible to catastrophic backtracking that could cause a DOS attack.

Weakness: CWE-1333

Which versions are affected by CVE-2021-39933?

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

Package	Affected	Fixed in
`gitlab` Bitnami	From `12.10.0`	`14.3.6, 14.4.4, 14.5.2`

Products include Gitlab Gitlab.

How do I fix CVE-2021-39933?

Upgrade gitlab to a fixed version for your release line: 14.3.6, 14.4.4 or 14.5.2.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2021-39933 being exploited?

There is no known exploitation of CVE-2021-39933 in the wild and no public exploit code.

All Gitlab Gitlab vulnerabilities

Sources

Also known as BIT-gitlab-2021-39933, GHSA-26gq-p245-cq98, UBUNTU-CVE-2021-39933.