Overview
In this post, we’ll discuss and delve into the details of a critical vulnerability, CVE-2025-2254, which affects GitLab CE/EE. This issue is prevalent in all versions from 17.9 before 17.10.8, 17.11 before 17.11.4, and 18.0 before 18.0.2. The vulnerability’s severity lies in its potential to allow Cross-Site Scripting (XSS) attacks due to improper output encoding in the snippet viewer functionality of GitLab. This vulnerability is of significant importance because an attacker exploiting it could potentially compromise the system or leak sensitive data.
Vulnerability Summary
CVE ID: CVE-2025-2254
Severity: High (8.7 CVSS Score)
Attack Vector: Network
Privileges Required: Low
User Interaction: Required
Impact: System compromise or data leakage upon successful exploit
Affected Products
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Product | Affected Versions
GitLab CE | 17.9 before 17.10.8
GitLab EE | 17.11 before 17.11.4, 18.0 before 18.0.2
How the Exploit Works
The exploit takes advantage of the improper output encoding in the snippet viewer functionality within GitLab. An attacker, by crafting a malicious snippet containing malicious script, can exploit this vulnerability to initiate a Cross-Site Scripting (XSS) attack. When an unsuspecting user views this malicious snippet, the embedded script is executed in the context of the user’s session. This could potentially allow the attacker to take over the user’s session, impersonate the user, and perform actions on their behalf.
Conceptual Example Code
Here’s a conceptual example of how the vulnerability might be exploited. This is an HTTP request where an attacker submits a malicious snippet to the vulnerable endpoint:
POST /snippets/create HTTP/1.1
Host: gitlab.example.com
Content-Type: application/json
{ "snippet_code": "<script>malicious_code_here</script>" }The malicious snippet contains a script tag with malicious code that could be executed when a user views the snippet.
Mitigation Guidance
The best course of action to mitigate this vulnerability is to apply the vendor-provided patch. GitLab has released patches for the affected versions which can be downloaded and applied. In cases where patching isn’t immediately feasible, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) could serve as temporary mitigation. These tools can help detect and block attempts to exploit this vulnerability.