CVE-2026-3988: Inefficient Algorithmic Complexity in GitLab

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-25 · updated 2026-06-17
Weakness: CWE-407

Description

GitLab has remediated an issue in GitLab CE/EE affecting all versions from 18.5 before 18.8.7, 18.9 before 18.9.3, and 18.10 before 18.10.1 that could have allowed an unauthenticated user to cause a denial of service by making the GitLab instance unresponsive due to improper input validation in GraphQL request processing.

Affected products

GitLab: from 18.5.0 before 18.8.7; from 18.9.0 before 18.9.3; 18.10.0 — fixed in 18.8.7, 18.9.3

How to fix

Upgrade to a fixed version: GitLab 18.8.7, 18.9.3. Check the vendor advisory for mitigations.

References

https://about.gitlab.com/releases/2026/03/25/patch-release-gitlab-18-10-1-released/
https://gitlab.com/gitlab-org/gitlab/-/work_items/593140
https://hackerone.com/reports/3597342

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