CVE-2007-3847 in HTTP Server
Summary
by MITRE
The date handling code in modules/proxy/proxy_util.c (mod_proxy) in Apache 2.3.0, when using a threaded MPM, allows remote origin servers to cause a denial of service (caching forward proxy process crash) via crafted date headers that trigger a buffer over-read.
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Analysis
by VulDB Data Team • 07/25/2019
The vulnerability described in CVE-2007-3847 represents a critical buffer over-read issue within Apache's mod_proxy module that specifically affects threaded Multi-Processing Modules. This flaw exists in the date handling code located in modules/proxy/proxy_util.c and manifests when Apache 2.3.0 operates with threaded MPM configurations. The vulnerability arises from inadequate input validation and memory management when processing date headers from remote origin servers, creating a scenario where maliciously crafted date values can trigger memory corruption.
The technical implementation of this vulnerability stems from improper bounds checking during date parsing operations within the proxy utility module. When a threaded MPM processes requests through a forward proxy configuration, the mod_proxy component attempts to parse date headers from upstream servers without sufficient validation of header content length or format. This allows an attacker controlling the origin server to craft date headers that exceed allocated buffer boundaries, resulting in memory over-read conditions that can corrupt adjacent memory regions and ultimately cause process crashes. The vulnerability is particularly dangerous in caching forward proxy configurations where multiple requests are processed through shared memory spaces.
The operational impact of this vulnerability extends beyond simple service disruption to encompass potential system stability compromise and denial of service conditions that can affect entire proxy infrastructure. When exploited, the buffer over-read causes the caching forward proxy process to terminate unexpectedly, requiring system administrators to restart affected services and potentially disrupting legitimate user access to proxy resources. The threaded nature of the MPM configuration amplifies the impact as multiple concurrent requests can trigger cascading failures across the proxy processing threads, making this vulnerability particularly effective for coordinated denial of service attacks against proxy servers.
This vulnerability maps to CWE-121, Buffer Overflow in Stack, and CWE-125, Out-of-bounds Read, while also aligning with ATT&CK techniques such as T1499.004, Endpoint Denial of Service, and T1595.001, Network Denial of Service. The attack vector requires a remote origin server to craft malicious date headers that can be processed by the vulnerable Apache proxy configuration, making it a sophisticated attack requiring both network access and knowledge of the target system's proxy implementation. Organizations should implement immediate mitigations including upgrading to patched Apache versions, implementing strict header validation policies, and configuring robust monitoring for anomalous date header patterns that could indicate exploitation attempts.