CVE-2010-0408 in HTTP Server
Summary
by MITRE
The ap_proxy_ajp_request function in mod_proxy_ajp.c in mod_proxy_ajp in the Apache HTTP Server 2.2.x before 2.2.15 does not properly handle certain situations in which a client sends no request body, which allows remote attackers to cause a denial of service (backend server outage) via a crafted request, related to use of a 500 error code instead of the appropriate 400 error code.
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Analysis
by VulDB Data Team • 05/01/2026
The vulnerability described in CVE-2010-0408 affects the Apache HTTP Server version 2.2.x before 2.2.15, specifically within the mod_proxy_ajp module. This module facilitates communication between Apache and backend application servers using the Apache JServ Protocol, which is commonly used to connect Apache with application servers like Apache Tomcat. The flaw resides in the ap_proxy_ajp_request function within mod_proxy_ajp.c, where improper handling occurs when clients send requests without request bodies. This particular issue represents a denial of service vulnerability that can be exploited remotely by attackers who craft specific requests designed to trigger the problematic code path. The vulnerability stems from the module's incorrect error handling behavior, where it responds with a 500 internal server error code instead of the more appropriate 400 bad request error code when encountering malformed requests without request bodies. This improper error code usage creates a condition where backend servers can become overwhelmed or crash, leading to service disruption. According to CWE classification, this vulnerability maps to CWE-20: Improper Input Validation, as it involves the server's failure to properly validate and handle client input, specifically request body presence. The issue also aligns with ATT&CK technique T1499.004: Network Denial of Service, as it enables attackers to cause availability issues in network services. The operational impact of this vulnerability is significant as it allows remote attackers to potentially bring down backend application servers through carefully crafted requests that exploit the flawed error handling logic. When the mod_proxy_ajp module encounters a request without a body, it fails to properly validate the request structure, leading to the backend server being subjected to malformed requests that it cannot process correctly. This creates a cascading effect where the backend server may become unresponsive or crash entirely, effectively causing a denial of service condition that impacts legitimate users. The vulnerability is particularly dangerous in environments where Apache serves as a reverse proxy for application servers, as it can be exploited to target the entire application infrastructure rather than just the web server itself. The root cause of this issue lies in the module's lack of proper validation for request completeness, particularly when dealing with requests that should contain a body but do not. This oversight in input validation creates an exploitable condition where attackers can manipulate the request flow to trigger the specific code path that leads to backend server instability. The vulnerability demonstrates a classic example of how improper error handling can lead to security consequences beyond simple data exposure, as it directly impacts system availability. Organizations using Apache HTTP Server with mod_proxy_ajp functionality are particularly at risk, especially those with high-traffic applications that rely on backend servers for processing requests. The exploitation of this vulnerability requires minimal technical skill and can be automated, making it a particularly attractive target for malicious actors seeking to disrupt services. The fix for this vulnerability involved updating the mod_proxy_ajp module to properly validate request structures and return appropriate error codes when malformed requests are encountered, specifically ensuring that requests without required bodies receive 400 error codes rather than 500 error codes that can cause backend server instability. This update addresses the core validation issue and prevents the exploitation vector that leads to the denial of service condition. Security practitioners should note that this vulnerability highlights the importance of proper input validation and error handling in proxy modules, as these components often serve as critical pathways for traffic between clients and backend systems, making them prime targets for exploitation. The vulnerability also demonstrates how seemingly minor error handling issues in web server modules can have significant operational impacts, particularly when they interact with backend systems that may not be designed to handle malformed requests gracefully.