CVE-2018-19571 in Community Edition
Summary
by MITRE
GitLab CE/EE, versions 8.18 up to 11.x before 11.3.11, 11.4 before 11.4.8, and 11.5 before 11.5.1, are vulnerable to an SSRF vulnerability in webhooks.
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Analysis
by VulDB Data Team • 09/03/2025
The vulnerability identified as CVE-2018-19571 represents a critical server-side request forgery flaw affecting GitLab Community Edition and Enterprise Edition across multiple version ranges. This vulnerability specifically impacts the webhook functionality within GitLab, which serves as a crucial integration mechanism for automating workflows and connecting external systems to the GitLab platform. The SSRF vulnerability arises from inadequate input validation and sanitization when processing webhook requests, allowing malicious actors to manipulate the system's behavior by forcing it to make unintended requests to internal or external resources. The affected versions span from 8.18 through 11.x, with specific patches released for 11.3.11, 11.4.8, and 11.5.1, indicating the severity and widespread nature of this flaw across the GitLab product line.
The technical implementation of this vulnerability stems from how GitLab handles webhook URLs and requests, particularly when processing incoming webhook payloads from external services. When a user configures a webhook within GitLab, the system is designed to send HTTP requests to the specified URL to notify external systems of events such as pushes, merge requests, or issue updates. However, the vulnerability occurs when the webhook URL processing logic fails to properly validate or sanitize the target URLs, allowing attackers to craft malicious webhook configurations that can force GitLab to make requests to internal network resources or external malicious servers. This flaw can be exploited through various attack vectors including direct manipulation of webhook settings, or by compromising a repository or project where an attacker can modify webhook configurations. The vulnerability falls under CWE-918, Server-Side Request Forgery, which is classified as a critical security weakness in web applications. From an operational perspective, this vulnerability represents a significant risk as it allows attackers to potentially bypass network security controls, access internal services, or even exfiltrate sensitive data from within the organization's network perimeter.
The operational impact of CVE-2018-19571 extends beyond simple data exfiltration or unauthorized access, as it can enable attackers to perform reconnaissance activities within the internal network and potentially escalate privileges through further exploitation. An attacker who successfully exploits this vulnerability can use it to scan internal network services, access internal APIs, or even establish command and control channels through the webhook functionality. The attack surface is particularly concerning given that GitLab is widely used in enterprise environments where it often serves as a central integration point for development workflows, CI/CD pipelines, and various automation tools. This vulnerability aligns with ATT&CK technique T1071.004, Application Layer Protocol: DNS, and T1071.001, Application Layer Protocol: Web Protocols, as it leverages legitimate application protocols to perform malicious activities. Organizations utilizing GitLab in production environments should consider this vulnerability as a high-priority issue requiring immediate remediation, as it can be exploited by attackers with minimal privileges to gain significant network access. The vulnerability also demonstrates the importance of proper input validation and the principle of least privilege in web application security, as the flaw could be exploited through simple configuration changes that do not require elevated system access.
Mitigation strategies for CVE-2018-19571 should focus on immediate patching of affected GitLab installations to the recommended versions 11.3.11, 11.4.8, and 11.5.1, which contain the necessary security fixes. Organizations should also implement additional controls including network segmentation to limit access to internal resources from GitLab servers, implementing strict firewall rules to prevent outbound connections from GitLab instances to internal services, and monitoring webhook activity for suspicious patterns. Security teams should conduct thorough reviews of all webhook configurations within their GitLab instances, ensuring that only trusted external services are configured as webhook endpoints. Additional defensive measures include implementing webhook request validation, rate limiting for webhook processing, and logging all webhook activity for security monitoring purposes. The vulnerability highlights the necessity of implementing comprehensive security testing practices including penetration testing and code review processes that specifically target input validation and request handling mechanisms within web applications. Organizations should also consider implementing automated security scanning tools that can detect similar vulnerabilities in their GitLab installations and other web applications to prevent future exploitation of similar flaws.