Overview
CVE-2025-12653 describes a security vulnerability in GitLab Community Edition (CE) and Enterprise Edition (EE) that could allow an unauthenticated user to join arbitrary organizations. This vulnerability affects versions 18.3 before 18.4.5, 18.5 before 18.5.3, and 18.6 before 18.6.1. By manipulating request headers under specific conditions, an attacker could bypass authentication checks and gain unauthorized access to an organization within GitLab.
Technical Details
The vulnerability stems from insufficient validation of request headers during the organization join process. An unauthenticated user could potentially modify certain headers in a crafted request to impersonate an authorized user or bypass authorization checks altogether. The specific details of the header manipulation are further detailed in the referenced issue and HackerOne report.
The vulnerability resides in the handling of the join organization requests, where insufficient validation of the Origin or Referer headers allows attackers to forge requests and gain unauthorized access.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) score for CVE-2025-12653 is 6.5 (MEDIUM).
This score reflects the following characteristics:
- Attack Vector (AV): Network
- Attack Complexity (AC): Low
- Privileges Required (PR): None
- User Interaction (UI): None
- Scope (S): Unchanged
- Confidentiality Impact (C): None
- Integrity Impact (I): Low
- Availability Impact (A): None
The MEDIUM severity indicates that while the vulnerability is exploitable, the impact is limited. An attacker can gain unauthorized access to an organization, potentially leading to data modification or other actions within that specific organization. The lack of Confidentiality and Availability impact lowers the overall CVSS score.
Possible Impact
Successful exploitation of CVE-2025-12653 could have the following consequences:
- Unauthorized Access: An attacker could gain access to an organization without proper authentication.
- Data Modification: The attacker may be able to modify data or configurations within the compromised organization, depending on their assigned role (which might default to a low-privileged one).
- Account Manipulation: Potentially escalate privileges within the organization depending on the existing roles and permissions model.
Mitigation and Patch Steps
GitLab has released patches to address this vulnerability. Users of GitLab CE/EE versions 18.3, 18.5, and 18.6 are strongly advised to upgrade to the following versions or later:
- Upgrade to 18.4.5 or higher if you are on the 18.3.x branch.
- Upgrade to 18.5.3 or higher if you are on the 18.5.x branch.
- Upgrade to 18.6.1 or higher if you are on the 18.6.x branch.
To upgrade your GitLab instance, follow the official GitLab upgrade documentation. Ensure you have a backup of your data before performing the upgrade.
References
- CVE ID: CVE-2025-12653
- GitLab Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/579372
- HackerOne Report: https://hackerone.com/reports/3370245
