Executive Summary

This vulnerability affects the Ghost Node.js content management system versions from 5.46.1 until 6.21.2. The issue is that the validation applied to filters on the public API endpoints could be partially bypassed. This bypass allows an attacker to reveal private fields through a brute force attack.

If the system uses SQLite as the database, password hashes are fully accessible. If MySQL is used, the password hashes lose their case sensitivity (uppercase/lowercase), which likely makes further brute force attacks on those hashes ineffective.

The vulnerability was fixed in version 6.21.2.

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Compliance Impact

The vulnerability in Ghost's Content API allows unauthorized access to private fields, including password hashes, which constitutes exposure of sensitive information.

Such exposure of sensitive personal data could negatively impact compliance with data protection regulations like GDPR and HIPAA, which require strict controls to protect personal and sensitive information from unauthorized access.

Organizations using affected versions of Ghost without applying the patch or mitigations may risk non-compliance due to this data exposure vulnerability.

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Detection Guidance

This vulnerability can be detected by monitoring and analyzing requests to the Ghost Content API endpoints for unusual or brute force attempts to access private fields such as password hashes or email addresses.

A practical approach is to inspect logs or network traffic for repeated requests with filter parameters targeting sensitive fields.

Suggested commands include using tools like curl or wget to simulate requests, or using grep and other log analysis commands to detect suspicious access patterns.

• Use curl to test API endpoints for filter bypass attempts, e.g.: curl -X GET 'https://your-ghost-site.com/ghost/api/content/posts/?filter=password:exists'
• Search server logs for repeated requests containing sensitive filter parameters: grep -i 'filter=password' /var/log/ghost/access.log
• Use network monitoring tools like tcpdump or Wireshark to capture and analyze traffic to the Ghost Content API endpoints.

Additionally, implementing WAF or reverse proxy rules to block or alert on requests containing sensitive filters can help detect exploitation attempts.

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Impact Analysis

This vulnerability can lead to unauthorized disclosure of private fields via the public API, which may include sensitive information such as password hashes.

If SQLite is used, attackers can fully access password hashes, potentially enabling them to crack user passwords through brute force.

If MySQL is used, the password hashes lose case sensitivity, which likely reduces the effectiveness of brute force attacks on those hashes.

Overall, this could compromise user account security and privacy.

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Mitigation Strategies

The vulnerability is fixed in Ghost version 6.21.2. The immediate step to mitigate this vulnerability is to upgrade your Ghost installation to version 6.21.2 or later.

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