CVE-2021-22166 in Community Edition
Summary
by MITRE • 01/16/2021
An attacker could cause a Prometheus denial of service in GitLab 13.7+ by sending an HTTP request with a malformed method
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 02/14/2021
The vulnerability CVE-2021-22166 represents a critical denial of service weakness in GitLab's Prometheus integration that affects versions 13.7 and later. This flaw resides in how the system processes HTTP requests within its monitoring infrastructure, specifically when handling malformed HTTP method specifications. The issue stems from insufficient input validation mechanisms that fail to properly sanitize or reject malformed HTTP method identifiers sent by malicious actors. When Prometheus encounters such malformed requests, it triggers an unexpected behavior that leads to resource exhaustion or process termination, effectively disrupting the monitoring capabilities of GitLab instances.
The technical implementation of this vulnerability demonstrates a classic input validation failure that aligns with CWE-20, which addresses "Improper Input Validation" in software systems. The flaw occurs at the HTTP request parsing layer where the Prometheus component does not adequately verify the legitimacy of HTTP method identifiers before processing them. This weakness creates an opportunity for attackers to exploit the system through crafted HTTP requests that contain malformed method specifications, potentially causing the monitoring service to crash or become unresponsive. The vulnerability is particularly concerning because it operates at the protocol level, affecting the fundamental communication mechanisms that GitLab uses to gather and process system metrics.
From an operational impact perspective, this vulnerability enables attackers to execute remote denial of service attacks against GitLab installations that utilize Prometheus monitoring. The attack requires minimal sophistication as it only necessitates sending specially crafted HTTP requests containing malformed method identifiers. Once exploited, the vulnerability can cause significant disruption to monitoring operations, potentially masking other security incidents or making it difficult for administrators to detect genuine system issues. The service disruption affects not only the monitoring capabilities but can also impact the overall availability of GitLab services that depend on proper metric collection and reporting.
The attack vector for CVE-2021-22166 follows patterns consistent with ATT&CK technique T1499.004, which involves network denial of service attacks through resource exhaustion or system instability. This vulnerability specifically targets the availability aspect of the CIA triad by compromising the monitoring infrastructure that supports GitLab's operational security. Organizations using GitLab with Prometheus integration face significant risk as this vulnerability can be exploited without requiring authentication or elevated privileges, making it particularly dangerous in multi-tenant environments where attackers might target specific instances. The impact extends beyond immediate service disruption to potentially compromise incident response capabilities and forensic analysis due to the loss of monitoring data.
Mitigation strategies for CVE-2021-22166 should prioritize immediate patching of affected GitLab versions to remediate the input validation weakness in the Prometheus integration. Organizations should implement network-level protections such as web application firewalls that can detect and block malformed HTTP requests before they reach the vulnerable components. Additionally, administrators should configure rate limiting and request validation rules to prevent excessive or malformed requests from overwhelming the monitoring infrastructure. The implementation of proper input sanitization and validation mechanisms within the HTTP parsing layer represents the most effective long-term solution, aligning with security best practices outlined in OWASP Top Ten and NIST cybersecurity frameworks. Regular security assessments and penetration testing should be conducted to identify similar validation weaknesses in other components of the GitLab ecosystem and ensure comprehensive protection against similar attack vectors.