CVE-2021-22178 in Community Edition
Summary
by MITRE • 03/24/2021
An issue has been discovered in GitLab affecting all versions starting from 13.2. Gitlab was vulnerable to SRRF attack through the Prometheus integration.
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Analysis
by VulDB Data Team • 04/04/2021
The vulnerability identified as CVE-2021-22178 represents a significant security flaw in GitLab's Prometheus integration that exposes organizations to Server-Side Request Forgery attacks. This vulnerability affects all GitLab versions starting from 13.2, making it a widespread concern for organizations relying on GitLab's monitoring capabilities. The flaw specifically manifests through the integration with Prometheus metrics collection, creating an attack vector that allows malicious actors to manipulate HTTP requests originating from the GitLab server. Such vulnerabilities are particularly dangerous because they can enable attackers to bypass network security controls and access internal systems that would normally be protected from external network access. The SRRF attack leverages the legitimate functionality of GitLab's Prometheus integration to make unauthorized requests to internal services that the GitLab server can reach but external attackers cannot. This creates a scenario where attackers can potentially exfiltrate data, perform reconnaissance on internal infrastructure, or even escalate privileges within the network.
The technical implementation of this vulnerability stems from insufficient input validation and improper handling of user-supplied data within the Prometheus integration module. When GitLab processes metrics data from Prometheus, the application fails to properly sanitize or validate URLs that are used to fetch additional metrics or communicate with external endpoints. This allows an attacker to inject malicious URLs that point to internal services, effectively turning GitLab's legitimate monitoring functionality into a tool for lateral movement and data exfiltration. The vulnerability can be exploited through various means including crafted metric names, custom labels, or manipulated configuration parameters that are processed by the Prometheus integration. According to CWE classification, this vulnerability maps to CWE-918 which describes Server-Side Request Forgery vulnerabilities where attackers can manipulate the target of a server-side request. The attack pattern aligns with ATT&CK technique T1071.004 which covers application layer protocol: DNS, demonstrating how attackers can leverage legitimate protocols to bypass security controls. The vulnerability specifically affects GitLab's monitoring infrastructure and can be exploited without requiring authentication to the GitLab instance itself, making it particularly concerning for organizations with extensive monitoring deployments.
The operational impact of CVE-2021-22178 extends beyond simple data leakage, potentially enabling attackers to conduct comprehensive reconnaissance of internal network infrastructure. Organizations utilizing GitLab's Prometheus integration for monitoring their development environments, production systems, or cloud deployments face significant risk as attackers can leverage this vulnerability to discover internal services, databases, or other sensitive systems that are not directly exposed to the internet. The attack surface is particularly broad because GitLab servers often have access to internal networks and services that are not accessible from external networks, making them ideal targets for attackers seeking to expand their access within an organization. This vulnerability can facilitate more sophisticated attacks including privilege escalation, data exfiltration, or even the deployment of additional malicious tools within the internal network. The impact is amplified in environments where GitLab is used for CI/CD pipeline monitoring or where Prometheus metrics are configured to access internal APIs or services that contain sensitive information or administrative functions.
Organizations should implement immediate mitigations including updating to the latest stable GitLab version that contains the patch for this vulnerability, which was released as part of GitLab 13.10.1 and subsequent releases. Network segmentation and firewall rules should be implemented to restrict outbound connections from GitLab servers to internal services, particularly those that are not essential for monitoring operations. Input validation should be strengthened throughout the Prometheus integration module to ensure that all URLs and endpoint specifications are properly sanitized before processing. Organizations should also consider implementing network monitoring and anomaly detection to identify unusual outbound requests that may indicate exploitation attempts. The patch addresses the root cause by implementing proper URL validation and ensuring that GitLab's Prometheus integration cannot be manipulated to make unauthorized requests to internal services. Security teams should conduct comprehensive assessments of their GitLab installations to identify any custom configurations or third-party integrations that may also be vulnerable to similar attack patterns. Regular security audits of monitoring systems and their integration points are essential to prevent similar vulnerabilities from emerging in the future, particularly as organizations continue to expand their use of monitoring and observability platforms.