CVE-2022-2255 in mod_wsgi
Summary
by MITRE • 08/25/2022
A vulnerability was found in mod_wsgi. The X-Client-IP header is not removed from a request from an untrusted proxy, allowing an attacker to pass the X-Client-IP header to the target WSGI application because the condition to remove it is missing.
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Analysis
by VulDB Data Team • 05/13/2025
The vulnerability identified as CVE-2022-2255 resides within the mod_wsgi module, a widely deployed Apache HTTP Server module that provides a WSGI interface for Python web applications. This issue represents a critical security flaw that undermines the integrity of request handling mechanisms when proxy configurations are involved. The mod_wsgi module serves as a bridge between Apache and Python web applications, making it a prime target for attackers seeking to manipulate application behavior through crafted HTTP headers. When deployed in environments where untrusted proxies are present, the module fails to properly sanitize incoming requests by removing the X-Client-IP header, creating a potential vector for header injection attacks.
The technical root cause of this vulnerability stems from the absence of proper header validation and sanitization logic within the mod_wsgi module. Specifically, the module lacks the conditional logic necessary to remove the X-Client-IP header when requests originate from untrusted proxy servers. This header, when present in requests, typically contains IP address information that should be stripped when passing through intermediate proxies to prevent spoofing attacks. The flaw manifests when an attacker controls an untrusted proxy server that forwards requests to a vulnerable mod_wsgi application, allowing the malicious header to reach the target application. This behavior violates fundamental security principles of header sanitization and trust boundary management, as the module fails to distinguish between trusted and untrusted proxy sources.
The operational impact of this vulnerability extends beyond simple header manipulation, potentially enabling several attack vectors that could compromise application security. An attacker could exploit this weakness to spoof client IP addresses, bypass IP-based access controls, or manipulate application logic that relies on the X-Client-IP header for authentication or authorization decisions. The vulnerability particularly affects web applications that implement IP-based rate limiting, access control lists, or other security measures that depend on accurate client IP information. According to CWE-20, this represents a classic input validation flaw where insufficient sanitization of untrusted data leads to security consequences, while the ATT&CK framework categorizes this under T1071.004 for application layer protocol manipulation. The vulnerability becomes especially dangerous in environments where mod_wsgi applications handle sensitive data or implement critical security functions.
Mitigation strategies for CVE-2022-2255 require immediate attention from system administrators and security teams responsible for maintaining Apache servers with mod_wsgi modules. The primary solution involves upgrading to a patched version of mod_wsgi that properly implements header sanitization for untrusted proxy scenarios. Organizations should also implement additional security measures such as configuring trusted proxy lists, implementing proper header validation at the reverse proxy level, and monitoring for suspicious header patterns in application logs. Network administrators should consider implementing explicit header filtering rules at the load balancer or reverse proxy level to prevent the X-Client-IP header from reaching vulnerable applications. The vulnerability highlights the importance of maintaining up-to-date security configurations and implementing defense-in-depth strategies that protect against header injection attacks. Organizations should also conduct thorough security assessments of their Apache configurations to identify other potential header-related vulnerabilities that could be exploited in similar attack scenarios.