CVE-2011-3624 in Ruby
Summary
by MITRE
Various methods in WEBrick::HTTPRequest in Ruby 1.9.2 and 1.8.7 and earlier do not validate the X-Forwarded-For, X-Forwarded-Host and X-Forwarded-Server headers in requests, which might allow remote attackers to inject arbitrary text into log files or bypass intended address parsing via a crafted header.
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Analysis
by VulDB Data Team • 03/04/2025
The vulnerability identified as CVE-2011-3624 resides within the WEBrick::HTTPRequest component of Ruby versions 1.9.2 and earlier, including 1.8.7 and prior releases. This issue represents a significant security flaw that affects web servers running Ruby applications, particularly those utilizing the WEBrick HTTP server implementation. The vulnerability stems from inadequate validation of specific HTTP headers that are commonly used for proxy and load balancer configurations, creating a potential attack vector for malicious actors seeking to manipulate server behavior or compromise log integrity.
The technical flaw manifests in the improper handling of three specific HTTP headers: X-Forwarded-For, X-Forwarded-Host, and X-Forwarded-Server. These headers are typically used by reverse proxies and load balancers to communicate information about the original client IP address, host name, and server identifier to the backend application. However, the WEBrick implementation fails to properly validate or sanitize these headers before processing them, allowing attackers to inject arbitrary content that gets interpreted by the server's logging mechanisms or address parsing functions. This lack of input validation creates opportunities for attackers to manipulate how the server interprets client information and logs client data.
The operational impact of this vulnerability extends beyond simple log file manipulation, as it can potentially enable attackers to bypass intended address parsing mechanisms and gain unauthorized access to server resources. When these headers are improperly handled, they can be exploited to inject malicious content into log files, which may subsequently be processed by other applications or tools that parse these logs. This creates a potential attack surface where attackers could manipulate audit trails or inject content that might be misinterpreted by security monitoring systems. The vulnerability particularly affects environments where Ruby-based web applications are deployed behind proxies or load balancers that rely on these headers to maintain proper client identification.
This vulnerability aligns with CWE-20, which describes improper input validation, and represents a classic case of insufficient sanitization of user-supplied data. The attack patterns associated with this flaw can be categorized under the ATT&CK framework as part of the "Command and Scripting Interpreter" and "Log Injection" techniques, where attackers leverage header manipulation to inject malicious content into server logs. The vulnerability also demonstrates characteristics consistent with CWE-119, which deals with weaknesses in memory management, as the improper handling of header data could potentially lead to memory corruption or unexpected behavior in applications that process these headers. Organizations deploying Ruby applications using WEBrick should prioritize patching this vulnerability to prevent potential exploitation that could lead to more severe security incidents.
Mitigation strategies for CVE-2011-3624 primarily involve upgrading to Ruby versions that contain patches for this vulnerability, specifically Ruby 1.9.3 or later, which address the improper header validation issue. Additionally, administrators should implement proper input validation at the application level and consider deploying web application firewalls that can detect and block malicious header content. Network-level protections such as proxy configurations that sanitize these headers before they reach the Ruby application can also provide defense-in-depth. Organizations should also review their logging mechanisms to ensure that log files are properly secured and that any content injected through these headers is appropriately sanitized before being processed by other systems that may interpret the log data.