CVE-2011-1498 in HttpClient
Summary
by MITRE
Apache HttpClient 4.x before 4.1.1 in Apache HttpComponents, when used with an authenticating proxy server, sends the Proxy-Authorization header to the origin server, which allows remote web servers to obtain sensitive information by logging this header.
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Analysis
by VulDB Data Team • 08/04/2024
The vulnerability described in CVE-2011-1498 represents a critical security flaw in Apache HttpClient 4.x versions prior to 4.1.1 that affects the handling of authentication headers when communicating through proxy servers. This issue stems from improper header management during HTTP request processing, where the client fails to properly distinguish between proxy authentication requirements and origin server authentication needs. The flaw specifically manifests when an authenticating proxy server is configured in the HTTP communication chain, creating a scenario where sensitive authentication information becomes inadvertently exposed to the final destination server.
The technical implementation of this vulnerability occurs at the HTTP protocol level within the Apache HttpClient library's request processing pipeline. When a client makes a request through an authenticating proxy, the HttpClient library correctly establishes proxy authentication using the Proxy-Authorization header. However, due to a design flaw in the library's header handling mechanism, this same Proxy-Authorization header is subsequently forwarded to the origin server as part of the request. This behavior violates fundamental security principles of authentication separation and creates an information disclosure vulnerability that can be exploited by malicious actors who control or can monitor the origin server.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable more sophisticated attacks within the network infrastructure. Remote web servers that receive requests containing the Proxy-Authorization header can log this information, creating persistent records of authentication credentials that were intended for proxy servers only. This exposure can lead to credential compromise, especially in environments where multiple proxies are used or where proxy authentication credentials have elevated privileges. The vulnerability is particularly concerning in enterprise environments where proxy authentication is commonly used for access control and network security policies, as it effectively undermines the security boundaries established by proxy configurations.
Security practitioners should note that this vulnerability aligns with CWE-200, which addresses information exposure, and demonstrates characteristics consistent with ATT&CK technique T1567.002 related to "Exfiltration Over Web Service." Organizations using Apache HttpClient 4.x should immediately upgrade to version 4.1.1 or later to remediate this issue, as the fix addresses the core header handling logic to ensure that proxy authentication headers are not forwarded to origin servers. Additionally, network administrators should implement monitoring for Proxy-Authorization headers in logs and consider implementing additional security controls such as network segmentation and proxy server hardening to reduce the attack surface and limit potential damage from credential exposure. The vulnerability underscores the importance of proper HTTP header management in security-critical applications and serves as a reminder of the potential consequences of inadequate separation of concerns in authentication protocols.