CVE-2021-39917

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-12-13 · updated 2026-06-17
Weakness: CWE-697

Description

An issue has been discovered in GitLab CE/EE affecting all versions starting from 12.9 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 related to quick actions features was susceptible to catastrophic backtracking that could cause a DOS attack.

Affected products

GitLab: from 12.9.0 before 14.3.6; from 14.4.0 before 14.4.4; from 14.5.0 before 14.5.2 — fixed in 14.3.6, 14.4.4, 14.5.2

How to fix

Upgrade to a fixed version: GitLab 14.3.6, 14.4.4, 14.5.2. Check the vendor advisory for mitigations.

References

https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39917.json
https://gitlab.com/gitlab-org/gitlab/-/issues/338486
https://hackerone.com/reports/1277918
https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39917.json
https://gitlab.com/gitlab-org/gitlab/-/issues/338486
https://hackerone.com/reports/1277918

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