CVE-2026-27603: Chartbrew Auth Bypass Vulnerability

CVE-2026-27603 Overview

CVE-2026-27603 is an authentication bypass vulnerability in Chartbrew, an open-source web application designed to connect directly to databases and APIs to create data visualizations. The vulnerability exists in versions prior to 4.8.4 where the chart filter endpoint POST /project/:project_id/chart/:chart_id/filter lacks both verifyToken and checkPermissions middleware, allowing unauthenticated users to access chart data from any team or project.

Critical Impact

Unauthenticated attackers can remotely access sensitive chart data across all teams and projects without any authentication, potentially exposing confidential business intelligence and analytics data.

Affected Products

• Depomo Chartbrew versions prior to 4.8.4
• Self-hosted Chartbrew installations without the security patch
• Any deployment exposing the chart filter API endpoint

Discovery Timeline

• 2026-03-06 - CVE-2026-27603 published to NVD
• 2026-03-10 - Last updated in NVD database

Technical Details for CVE-2026-27603

Vulnerability Analysis

This vulnerability is classified as CWE-306: Missing Authentication for Critical Function. The flaw exists in the application's API route handling where the chart filter endpoint was implemented without the standard authentication and authorization middleware that protects other endpoints in the application.

The vulnerable endpoint POST /project/:project_id/chart/:chart_id/filter processes requests to filter and retrieve chart data. Under normal circumstances, this endpoint should verify that the requesting user has a valid session token and appropriate permissions to access the specified project and chart resources. However, the absence of verifyToken and checkPermissions middleware allows any network-accessible request to retrieve chart data regardless of authentication status.

This represents a critical access control failure that could expose sensitive business data, metrics, and analytics information stored within Chartbrew dashboards to unauthorized parties.

Root Cause

The root cause of this vulnerability is the omission of authentication and authorization middleware on a sensitive API endpoint. During development, the verifyToken middleware (which validates user session tokens) and the checkPermissions middleware (which enforces role-based access control) were not applied to the chart filter route handler. This oversight left the endpoint publicly accessible without any access control mechanisms.

Attack Vector

The attack vector for CVE-2026-27603 is network-based and requires no user interaction or authentication. An attacker can exploit this vulnerability by sending crafted HTTP POST requests directly to the vulnerable endpoint.

The exploitation process involves:

1. Identifying a Chartbrew instance accessible over the network
2. Enumerating or guessing valid project and chart IDs
3. Sending unauthenticated POST requests to the /project/:project_id/chart/:chart_id/filter endpoint
4. Retrieving chart data from any team or project without authentication

Since no authentication is required, attackers can systematically iterate through project and chart IDs to extract data from multiple dashboards. The vulnerability requires network access to the target Chartbrew instance but no privileges or special conditions to exploit.

Detection Methods for CVE-2026-27603

Indicators of Compromise

• Unusual volume of requests to /project/*/chart/*/filter endpoints from unknown IP addresses
• Access logs showing successful responses to the chart filter endpoint without corresponding authenticated sessions
• API requests to chart filter endpoints that lack authentication headers or tokens
• Sequential or pattern-based requests attempting to enumerate project and chart IDs

Detection Strategies

• Monitor web server access logs for unauthenticated POST requests to chart filter endpoints
• Implement rate limiting alerts for excessive requests to chart-related API paths
• Review application logs for chart data access patterns without corresponding user authentication events
• Deploy web application firewall (WAF) rules to detect enumeration attempts against API endpoints

Monitoring Recommendations

• Enable detailed access logging for all Chartbrew API endpoints
• Configure alerts for high-volume requests to chart filter endpoints from single IP addresses
• Monitor for requests to the vulnerable endpoint pattern across your Chartbrew deployment
• Establish baseline metrics for normal chart filter API usage to identify anomalous activity

How to Mitigate CVE-2026-27603

Immediate Actions Required

• Upgrade Chartbrew to version 4.8.4 or later immediately
• Audit access logs for any historical exploitation attempts against the chart filter endpoint
• If upgrading is not immediately possible, restrict network access to the Chartbrew application
• Review any potentially exposed chart data for sensitive information that may have been compromised

Patch Information

The vulnerability has been addressed in Chartbrew version 4.8.4. The patch adds the missing verifyToken and checkPermissions middleware to the chart filter endpoint, ensuring that only authenticated users with appropriate permissions can access chart data.

For detailed patch information, refer to the GitHub Release v4.8.4 and the GitHub Security Advisory GHSA-9fhr-5vvc-p455.

Workarounds

• Implement network-level access controls to restrict access to Chartbrew from trusted networks only
• Deploy a reverse proxy with authentication requirements in front of the Chartbrew application
• Use firewall rules to block external access to the /project/*/chart/*/filter endpoint path
• Consider temporarily disabling the chart filter functionality if the feature is not critical to operations

# Example: Block access to vulnerable endpoint using nginx
location ~ ^/project/[^/]+/chart/[^/]+/filter$ {
    # Deny all access until patched
    deny all;
    return 403;
}