CVE-2021-28148: Grafana Enterprise DoS Vulnerability

CVE-2021-28148 Overview

CVE-2021-28148 is a missing authentication vulnerability affecting Grafana Enterprise that allows unauthenticated attackers to cause a denial of service condition. One of the usage insights HTTP API endpoints in Grafana Enterprise is accessible without any authentication, enabling any unauthenticated user to send an unlimited number of requests to the endpoint. This can lead to resource exhaustion and a denial of service (DoS) attack against vulnerable Grafana Enterprise instances.

Critical Impact

Unauthenticated remote attackers can render Grafana Enterprise instances unavailable by flooding an unprotected API endpoint with requests, disrupting monitoring and observability operations across the organization.

Affected Products

• Grafana Enterprise 6.x before 6.7.6
• Grafana Enterprise 7.x before 7.3.10
• Grafana Enterprise 7.4.x before 7.4.5

Discovery Timeline

• 2021-03-22 - CVE-2021-28148 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-28148

Vulnerability Analysis

This vulnerability is classified under CWE-306 (Missing Authentication for Critical Function). The core issue stems from an API endpoint within Grafana Enterprise's usage insights feature that fails to enforce authentication requirements. The endpoint is designed to collect and provide usage analytics data, but due to a missing authentication check, it remains accessible to any network user without requiring valid credentials.

The attack can be executed remotely over the network with low complexity. No privileges or user interaction are required to exploit this vulnerability. While the confidentiality and integrity of the system remain unaffected, the availability impact is significant, as attackers can exhaust server resources by flooding the unprotected endpoint with requests.

Root Cause

The root cause of CVE-2021-28148 is a missing authentication mechanism on the usage insights HTTP API endpoint. Grafana Enterprise's code path for this specific endpoint does not include the standard authentication middleware or access control checks that protect other API endpoints. This oversight allows the endpoint to process requests from any source without validating user identity or permissions.

Attack Vector

The attack vector is network-based, requiring only HTTP access to the vulnerable Grafana Enterprise instance. An attacker can exploit this vulnerability by:

1. Identifying a Grafana Enterprise instance exposed to the network
2. Locating the unprotected usage insights API endpoint
3. Sending a high volume of HTTP requests to exhaust server resources
4. Causing service degradation or complete denial of service for legitimate users

Since no authentication is required and there are no rate limiting controls on the vulnerable endpoint, attackers can sustain the attack indefinitely with minimal resources, making this a particularly effective DoS vector against exposed Grafana Enterprise deployments.

Detection Methods for CVE-2021-28148

Indicators of Compromise

• Unusual spike in HTTP requests targeting the usage insights API endpoint
• Increased server resource utilization (CPU, memory, network bandwidth) without corresponding legitimate user activity
• Access logs showing repeated requests to the vulnerable endpoint from external or unexpected IP addresses
• Service degradation or timeouts reported by Grafana users and dependent monitoring systems

Detection Strategies

• Implement web application firewall (WAF) rules to detect and alert on high-volume requests to Grafana API endpoints
• Configure intrusion detection systems (IDS) to monitor for DoS attack patterns targeting Grafana services
• Review Grafana access logs for unauthenticated requests to the usage insights endpoint
• Set up alerting on abnormal request rates to Grafana Enterprise API endpoints

Monitoring Recommendations

• Monitor server resource metrics (CPU, memory, network I/O) for Grafana Enterprise instances and alert on anomalies
• Implement rate limiting at the network perimeter or reverse proxy level for Grafana-bound traffic
• Enable detailed access logging for all Grafana API endpoints to facilitate forensic analysis
• Configure health check endpoints and automated alerting for Grafana service availability

How to Mitigate CVE-2021-28148

Immediate Actions Required

• Upgrade Grafana Enterprise to patched versions: 6.7.6, 7.3.10, or 7.4.5 or later immediately
• Restrict network access to Grafana Enterprise instances using firewall rules, allowing only trusted IP ranges
• Place Grafana Enterprise behind a reverse proxy with rate limiting and authentication enforcement
• Review access logs for any evidence of exploitation prior to patching

Patch Information

Grafana has released security updates that address this vulnerability. Organizations should upgrade to the following patched versions:

• Grafana Enterprise 6.x: Upgrade to version 6.7.6 or later
• Grafana Enterprise 7.0.x - 7.3.x: Upgrade to version 7.3.10 or later
• Grafana Enterprise 7.4.x: Upgrade to version 7.4.5 or later

For detailed patch information, refer to the Grafana Security Update Announcement and the Grafana Blog Security Fixes Overview.

Workarounds

• Implement network-level access controls to restrict access to Grafana Enterprise from untrusted networks
• Deploy a reverse proxy (e.g., nginx, HAProxy) in front of Grafana with rate limiting configured for all API endpoints
• Use a web application firewall (WAF) to block suspicious request patterns targeting the usage insights endpoint
• Temporarily disable the usage insights feature if possible until patching can be completed

# Example nginx rate limiting configuration for Grafana
limit_req_zone $binary_remote_addr zone=grafana_api:10m rate=10r/s;

server {
    listen 443 ssl;
    server_name grafana.example.com;
    
    location /api/ {
        limit_req zone=grafana_api burst=20 nodelay;
        proxy_pass http://grafana-backend:3000;
    }
}