CVE-2024-43409: Ghost CMS Auth Bypass Vulnerability

CVE-2024-43409 Overview

CVE-2024-43409 is an Improper Authentication vulnerability affecting Ghost, the popular open-source Node.js content management system. The vulnerability stems from improper authentication on certain endpoints used for member actions, allowing an attacker to perform member-only actions and read sensitive member information without proper authorization.

Critical Impact

Attackers can bypass authentication mechanisms to access member-only functionality and extract sensitive member data, potentially leading to unauthorized account manipulation and data exposure.

Affected Products

• Ghost versions v4.46.0 through v5.89.4
• Ghost CMS for Node.js deployments
• Self-hosted and managed Ghost installations running vulnerable versions

Discovery Timeline

• August 20, 2024 - CVE-2024-43409 published to NVD
• August 26, 2024 - Last updated in NVD database

Technical Details for CVE-2024-43409

Vulnerability Analysis

This vulnerability is classified under CWE-284 (Improper Access Control) and CWE-287 (Improper Authentication). The core issue lies in how Ghost handles authentication for member-related API endpoints. Certain endpoints that should require authenticated sessions were accessible without proper verification, creating a significant authentication bypass opportunity.

The vulnerability affects the member portal component of Ghost, specifically in how the application handles data fetching and member verification for newsletter management and account-related functionality. Without proper UUID verification on these endpoints, an attacker could invoke member actions that should be restricted to authenticated users only.

Root Cause

The root cause of CVE-2024-43409 is the absence of UUID verification on member endpoints that do not require a traditional session-based authentication. The fetchLinkData function in the portal application was not receiving the member context necessary to validate requests, allowing unauthenticated access to member-specific operations.

Additionally, the Account Email Page component lacked proper redirection logic for unauthenticated users attempting to access member-only functionality, and did not properly validate newsletter UUIDs before processing actions.

Attack Vector

The attack vector is network-based with low complexity, requiring no privileges or user interaction. An attacker can exploit this vulnerability by:

1. Identifying exposed Ghost member API endpoints
2. Crafting requests to member-action endpoints without providing valid authentication
3. Performing unauthorized member operations such as reading member information or modifying member preferences
4. Accessing newsletter management functionality without proper authorization

     async fetchData() {
         const {site: apiSiteData, member} = await this.fetchApiData();
         const {site: devSiteData, ...restDevData} = this.fetchDevData();
-        const {site: linkSiteData, ...restLinkData} = this.fetchLinkData(apiSiteData);
+        const {site: linkSiteData, ...restLinkData} = this.fetchLinkData(apiSiteData, member);
         const {site: previewSiteData, ...restPreviewData} = this.fetchPreviewData();
         const {site: notificationSiteData, ...restNotificationData} = this.fetchNotificationData();
         let page = '';

Source: GitHub Commit Details

Detection Methods for CVE-2024-43409

Indicators of Compromise

• Unexpected or unauthorized access to member API endpoints from external IP addresses
• Anomalous requests to /members/api/ endpoints without valid session cookies
• Unusual patterns of newsletter subscription changes or member data queries
• Access logs showing requests to member endpoints with missing or invalid authentication headers

Detection Strategies

• Monitor Ghost application logs for API requests to member endpoints that lack proper authentication tokens
• Implement rate limiting detection on member-related API endpoints to identify automated exploitation attempts
• Deploy web application firewall (WAF) rules to flag suspicious patterns targeting Ghost member functionality
• Review access logs for sequential enumeration attempts on member endpoints

Monitoring Recommendations

• Enable detailed logging for all Ghost member API interactions
• Set up alerts for failed authentication attempts on member endpoints followed by successful data access
• Monitor for bulk data extraction patterns that may indicate member information harvesting
• Track changes to newsletter subscriptions and member preferences for unauthorized modifications

How to Mitigate CVE-2024-43409

Immediate Actions Required

• Upgrade Ghost to version v5.89.5 or later immediately
• Audit recent access logs for signs of exploitation on member endpoints
• Review member data for unauthorized changes or access patterns
• Implement network-level access controls for Ghost admin and API endpoints

Patch Information

The Ghost development team has released version v5.89.5 which contains the security fix for this vulnerability. The patch adds proper UUID verification to member endpoints that do not require a session, ensuring that member context is properly validated before allowing access to sensitive operations. The fix modifies the fetchLinkData function to accept and validate member information, and enhances the Account Email Page to properly redirect unauthenticated users.

For detailed patch information, refer to the GitHub Security Advisory GHSA-78x2-cwp9-5j42 and the commit details.

Workarounds

• If immediate upgrade is not possible, restrict access to Ghost member API endpoints at the network or reverse proxy level
• Implement additional authentication layers using a reverse proxy or API gateway in front of Ghost
• Temporarily disable public member registration and newsletter features until the patch can be applied
• Monitor and log all member endpoint access while awaiting upgrade

# Configuration example for nginx to restrict member API access
location /members/api/ {
    # Restrict access to authenticated sessions only
    if ($http_cookie !~* "ghost-members-ssr") {
        return 403;
    }
    proxy_pass http://ghost_backend;
}