IP Spoofing via X-Forwarded-For in Ghost CLI

Executive Summary

Ghost CLI before 1.30.1 has an IP spoofing vulnerability where unauthenticated remote attackers can bypass rate-limiting by manipulating the X-Forwarded-For header. This is possible due to a misconfigured Nginx setup using the $proxy_add_x_forwarded_for directive, allowing attackers to insert arbitrary IP addresses to evade Ghost's rate-limiting protections on self-hosted instances.

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Detection Guidance

Check Nginx configuration files for the use of $proxy_add_x_forwarded_for directive in proxy settings. Inspect HTTP headers in requests to Ghost instances for X-Forwarded-For values that include appended IP addresses. Monitor rate-limiting logs for unusual patterns or bypass attempts.

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Impact Analysis

This vulnerability could allow attackers to overload your Ghost instance by bypassing rate limits, potentially causing service disruptions or increased resource usage. It may also enable abuse of your system for spam or other malicious activities under a false IP identity.

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Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by allowing unauthorized access or manipulation of rate-limiting controls. If exploited, it may enable attackers to bypass security measures that protect user data, leading to unauthorized access or data exfiltration. This could result in violations of data protection requirements under these regulations.

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Mitigation Strategies

Upgrade Ghost CLI to version 1.30.1 or later. Review and correct Nginx configurations to avoid using $proxy_add_x_forwarded_for in proxy_pass directives. Implement strict input validation for X-Forwarded-For headers on the application side.

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