CVE-2025-2256: Improper Validation of Specified Quantity in Input 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: 2025-09-12 · updated 2026-10-19
Weakness: CWE-1284

Description

An issue has been discovered in GitLab CE/EE affecting all versions from 7.12 before 18.1.6, 18.2 before 18.2.6, and 18.3 before 18.3.2 that could have allowed unauthorized users to render the GitLab instance unresponsive to legitimate users by sending multiple concurrent large SAML responses.

Affected products

GitLab: from 7.12.0 before 18.1.6; from 18.2.0 before 18.2.6; from 18.3.0 before 18.3.2 — fixed in 18.1.6, 18.2.6, 18.3.2

How to fix

Upgrade to a fixed version: GitLab 18.1.6, 18.2.6, 18.3.2. Check the vendor advisory for mitigations.

References

https://about.gitlab.com/releases/2025/09/10/patch-release-gitlab-18-3-2-released/
https://gitlab.com/gitlab-org/gitlab/-/issues/524633
https://hackerone.com/reports/3019485

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