CVE-2011-3187 in Ruby on Rails
Summary
by MITRE
The to_s method in actionpack/lib/action_dispatch/middleware/remote_ip.rb in Ruby on Rails 3.0.5 does not validate the X-Forwarded-For header in requests from IP addresses on a Class C network, which might allow remote attackers to inject arbitrary text into log files or bypass intended address parsing via a crafted header.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 03/07/2025
The vulnerability described in CVE-2011-3187 resides within the Ruby on Rails framework's handling of HTTP request headers, specifically in the actionpack component responsible for managing IP address information. This flaw affects version 3.0.5 of the framework and stems from improper validation of the X-Forwarded-For header, a common HTTP header used to identify the original IP address of a client connecting through a proxy or load balancer. The vulnerability manifests when processing requests from IP addresses within Class C network ranges, which typically encompass 256 IP addresses per network segment. The core issue lies in the to_s method implementation within action_dispatch/middleware/remote_ip.rb, where the framework fails to properly validate or sanitize the X-Forwarded-For header content before using it for address parsing.
The technical flaw represents a classic case of insufficient input validation and header sanitization, categorized under CWE-20 as "Improper Input Validation." When a malicious actor crafts a specially formatted X-Forwarded-For header containing arbitrary text, the vulnerable Rails application processes this input without adequate validation, leading to potential security implications. The vulnerability specifically targets the parsing logic that determines client IP addresses, which is crucial for applications that rely on accurate IP tracking for logging, access control, or security monitoring purposes. The flaw does not directly enable code execution or data compromise but creates conditions where attackers can manipulate how IP addresses are interpreted and logged within the application infrastructure.
The operational impact of this vulnerability extends beyond simple log file manipulation, creating potential attack vectors for bypassing intended security measures and conducting log injection attacks. Attackers can exploit this weakness to insert malicious content into application logs, potentially obscuring legitimate activities or creating confusion during security incident investigations. The ability to inject arbitrary text into log files represents a significant concern for security operations teams that depend on accurate logging for threat detection and forensic analysis. Additionally, the vulnerability undermines the integrity of IP address information used for access control, potentially allowing unauthorized access to resources that should be restricted based on IP address validation. This type of vulnerability aligns with ATT&CK technique T1070.002 for "Indicator Removal on Host: File Deletion" and T1566.002 for "Phishing: Spearphishing Attachment" when considering how attackers might leverage such weaknesses to hide their activities or establish persistence.
Mitigation strategies for CVE-2011-3187 require immediate application of the vendor-provided patch or upgrade to a non-vulnerable version of Ruby on Rails. Organizations should implement proper header validation mechanisms that sanitize and validate all incoming X-Forwarded-For headers before processing them within the application framework. Security teams should also configure their logging systems to properly escape or filter log entries to prevent injection attacks from corrupting audit trails. Network-level protections can include implementing strict header validation at load balancers or reverse proxies to ensure that only properly formatted IP addresses are passed to backend applications. The vulnerability highlights the importance of maintaining up-to-date security practices and demonstrates how seemingly minor implementation flaws in core framework components can create significant security risks across entire application ecosystems. Organizations should conduct thorough security assessments of their Ruby on Rails applications to identify similar vulnerabilities in header processing and validation logic.