CVE-2025-3454: Grafana Auth Bypass Vulnerability

CVE-2025-3454 Overview

This vulnerability in Grafana's datasource proxy API allows authorization checks to be bypassed by adding an extra slash character in the URL path. Users with minimal permissions could gain unauthorized read access to GET endpoints in Alertmanager and Prometheus datasources. The issue primarily affects datasources that implement route-specific permissions, including Alertmanager and certain Prometheus-based datasources.

Critical Impact

Attackers with low-privilege access can bypass authorization controls and gain unauthorized read access to sensitive monitoring data in Alertmanager and Prometheus datasources by manipulating URL paths.

Affected Products

• Grafana (versions with datasource proxy API)
• Alertmanager datasources
• Prometheus-based datasources with route-specific permissions

Discovery Timeline

• 2025-06-02 - CVE-2025-3454 published to NVD
• 2025-06-02 - Last updated in NVD database

Technical Details for CVE-2025-3454

Vulnerability Analysis

This authorization bypass vulnerability (CWE-285: Improper Authorization) exists in Grafana's datasource proxy API. The flaw stems from improper handling of URL path normalization, where the addition of an extra slash character (/) in the request path allows attackers to circumvent route-specific authorization checks.

When Grafana processes requests to datasource proxy endpoints, it performs authorization validation against defined routes. However, the authorization logic fails to properly normalize URL paths before matching them against permission rules. This discrepancy allows authenticated users with minimal privileges to craft requests that bypass intended access controls.

The vulnerability is network-accessible and requires only low-level authentication to exploit. While the scope is changed (affecting resources beyond the vulnerable component), the impact is limited to confidentiality through unauthorized read access to GET endpoints.

Root Cause

The root cause is improper authorization validation in Grafana's datasource proxy API. The authorization mechanism does not adequately normalize or sanitize URL paths before performing permission checks. When an attacker appends an additional slash character to the URL path, the authorization logic fails to recognize the modified path as requiring elevated permissions, while the underlying routing mechanism still processes the request successfully.

This is a classic path normalization bypass where different components interpret URL paths differently—the authorization layer sees one path while the routing layer interprets another.

Attack Vector

The attack vector is network-based and requires an authenticated user with minimal permissions on the Grafana instance. An attacker exploits this vulnerability by:

1. Identifying protected GET endpoints in Alertmanager or Prometheus datasources
2. Crafting malicious requests with an additional slash character in the URL path
3. Sending the modified request through the datasource proxy API
4. Bypassing authorization checks to access restricted data

The vulnerability enables unauthorized read access to monitoring configuration and alert data that should be restricted to privileged users.

Detection Methods for CVE-2025-3454

Indicators of Compromise

• Unusual URL patterns in access logs containing double slashes (//) in datasource proxy paths
• Low-privilege users accessing Alertmanager or Prometheus endpoints they should not have permission to view
• Anomalous GET request patterns to /api/datasources/proxy/ endpoints
• Access log entries showing successful responses to malformed URL paths

Detection Strategies

• Monitor Grafana access logs for URL paths containing consecutive slashes in datasource proxy requests
• Implement web application firewall (WAF) rules to detect and flag path traversal patterns
• Configure alerting on authorization audit logs for access anomalies to datasource endpoints
• Review user access patterns to identify potential exploitation attempts

Monitoring Recommendations

• Enable verbose logging for Grafana's datasource proxy API
• Deploy network monitoring to detect anomalous request patterns to Grafana endpoints
• Implement SIEM rules to correlate low-privilege user activity with access to restricted datasource endpoints
• Regularly audit user permissions and access logs for Alertmanager and Prometheus datasources

How to Mitigate CVE-2025-3454

Immediate Actions Required

• Review and apply security patches from Grafana when available
• Audit current user permissions and restrict unnecessary access to datasource configurations
• Implement WAF rules to normalize and sanitize URL paths before they reach Grafana
• Monitor access logs for signs of exploitation attempts

Patch Information

Grafana has released a security advisory addressing this vulnerability. Administrators should consult the Grafana Security Advisory CVE-2025-3454 for specific patch versions and upgrade instructions. Apply the latest security updates as soon as possible to remediate this authorization bypass vulnerability.

Workarounds

• Implement reverse proxy or WAF rules to normalize URL paths and block requests with consecutive slashes
• Restrict network access to Grafana instances to trusted networks only
• Review and minimize user permissions, applying principle of least privilege
• Disable or restrict access to affected Alertmanager and Prometheus datasources until patching is complete
• Enable additional authentication controls for datasource proxy endpoints

# Example nginx configuration to normalize URL paths
# Add to your Grafana reverse proxy configuration
merge_slashes on;

# Block requests with double slashes to datasource proxy
location ~* /api/datasources/proxy/.*//.* {
    return 403;
}