CVE-2004-1834 in HTTP Server
Summary
by MITRE
mod_disk_cache in Apache 2.0 through 2.0.49 stores client headers, including authentication information, on the hard disk, which could allow local users to gain sensitive information.
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Analysis
by VulDB Data Team • 05/26/2019
The vulnerability described in CVE-2004-1834 represents a critical security flaw in Apache's mod_disk_cache module that existed in versions 2.0 through 2.0.49. This issue fundamentally undermines the security assumptions of web server caching mechanisms by creating an unintended data exposure channel. The mod_disk_cache module was designed to improve performance by storing frequently requested content on disk, but it failed to properly sanitize the cached data before writing it to persistent storage. This oversight created a scenario where sensitive authentication headers, including credentials and session tokens, could be inadvertently stored in plain text within the server's cache directories, making them accessible to any local user with file system access.
The technical implementation of this vulnerability stems from the module's failure to properly filter HTTP headers before cache storage operations. When Apache processes requests that include authentication headers such as Authorization, Cookie, or other sensitive metadata, the mod_disk_cache module indiscriminately stores these headers along with the cached content. This behavior violates fundamental security principles of data separation and access control, as the cached files become repositories of authentication material that should remain protected. The vulnerability specifically impacts the cache storage mechanism where HTTP responses are written to disk, with the authentication headers being serialized alongside the response body and other metadata. This flaw is categorized under CWE-200, Information Exposure, and represents a classic example of how caching mechanisms can introduce security risks when not properly designed with security considerations in mind.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates persistent exposure windows for authentication data that can be exploited by local attackers. Any user with access to the file system where Apache's cache directories are stored can directly read cached files and extract sensitive information from the stored headers. This includes not only authentication tokens but also session identifiers, personal identification data, and potentially other confidential information transmitted in HTTP headers. The vulnerability is particularly concerning in multi-user environments where local privilege escalation or unauthorized access to system accounts could provide attackers with access to cached authentication data. From an attack perspective, this vulnerability aligns with ATT&CK technique T1552.001, "Unsecured Credentials," as it represents an unsecured storage scenario where authentication information is persistently stored without proper protection mechanisms.
The mitigation strategy for this vulnerability requires immediate patching of affected Apache installations to versions that properly sanitize cached content or disable the problematic caching behavior. System administrators should implement proper file system permissions and access controls on Apache cache directories to limit local user access to cached files. Additionally, organizations should consider implementing monitoring solutions to detect unauthorized access to cache directories and establish regular audit procedures to identify and remove cached sensitive data. The vulnerability highlights the importance of security reviews during feature development and demonstrates why caching mechanisms must be designed with explicit security controls to prevent information leakage. Organizations should also consider implementing alternative caching strategies that do not store sensitive headers or employ encryption for cached content to prevent similar issues in future deployments.