CVE-2007-3947 in lighttpd
Summary
by MITRE
request.c in lighttpd 1.4.15 allows remote attackers to cause a denial of service (daemon crash) by sending an HTTP request with duplicate headers, as demonstrated by a request containing two Location header lines, which results in a segmentation fault.
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Analysis
by VulDB Data Team • 07/21/2021
The vulnerability identified as CVE-2007-3947 affects lighttpd version 1.4.15 and represents a denial of service flaw stemming from improper handling of HTTP requests containing duplicate headers. This issue manifests when the web server processes requests with multiple instances of the same header field, specifically demonstrated through requests containing two Location header lines. The flaw resides in the request.c file of the lighttpd software, which fails to properly validate or process duplicate header occurrences during HTTP request parsing. When such malformed requests are received, the server encounters a segmentation fault that causes the daemon to crash and terminate its operation.
The technical implementation of this vulnerability demonstrates a classic buffer management or parsing error where the software does not adequately check for duplicate header fields during request processing. When duplicate headers are encountered, the internal data structures or parsing routines likely attempt to process these headers in a manner that leads to memory corruption or invalid pointer dereferencing. The Location header is particularly significant in this context as it is commonly used in HTTP redirects and is often processed with specific handling logic that may not account for duplicate occurrences. This flaw falls under the category of improper input validation and can be classified as a CWE-129 vulnerability related to insufficient validation of the length or number of input data elements.
From an operational perspective, this vulnerability presents a significant risk to web server availability as remote attackers can exploit it to cause service disruption without requiring authentication or specialized privileges. The impact extends beyond simple denial of service as the daemon crash can result in complete service unavailability until manual restart occurs, potentially affecting all websites hosted on the affected server. The vulnerability is particularly concerning in environments where lighttpd serves as a primary web server and where automated monitoring systems may not immediately detect the service interruption. The exploitability is straightforward as attackers only need to craft HTTP requests with duplicate headers, making this a low-effort, high-impact attack vector.
Security practitioners should consider this vulnerability in the context of the ATT&CK framework under the T1499.004 technique for network denial of service, where adversaries exploit software weaknesses to disrupt services. The vulnerability also aligns with T1595.001 for reconnaissance activities where attackers might probe for such flaws before launching more sophisticated attacks. Mitigation strategies should include immediate patching of lighttpd installations to versions that properly handle duplicate headers, implementing rate limiting on incoming requests to prevent abuse, and deploying intrusion detection systems that can identify malformed HTTP requests. Additionally, organizations should consider implementing web application firewalls that can filter out requests containing duplicate headers before they reach the web server. The fix typically involves modifying the request parsing logic to properly handle duplicate header fields without causing memory corruption or segmentation faults, ensuring that the server maintains stability even when processing malformed input.