CVE-2008-4298 in lighttpd
Summary
by MITRE
Memory leak in the http_request_parse function in request.c in lighttpd before 1.4.20 allows remote attackers to cause a denial of service (memory consumption) via a large number of requests with duplicate request headers.
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Analysis
by VulDB Data Team • 08/02/2021
The vulnerability identified as CVE-2008-4298 represents a critical memory management flaw within the lighttpd web server software, specifically affecting versions prior to 1.4.20. This issue resides in the http_request_parse function located within the request.c source file, where improper handling of request headers leads to systematic memory accumulation during HTTP request processing. The flaw manifests when the server receives multiple HTTP requests containing duplicate header fields, causing the application to allocate memory for each header without properly releasing previously allocated resources. This behavior creates a progressive memory consumption pattern that can ultimately exhaust available system memory resources.
The technical implementation of this vulnerability demonstrates a classic memory leak pattern where the lighttpd server fails to properly manage dynamic memory allocations during HTTP request parsing. When duplicate headers are encountered in incoming requests, the parsing function repeatedly allocates memory for header structures without performing necessary cleanup operations. This issue directly maps to CWE-401, which categorizes memory leaks as a fundamental weakness in software design that leads to resource exhaustion. The vulnerability operates at the application layer of the OSI model, specifically within the HTTP protocol handling mechanisms of the web server software. Attackers can exploit this flaw by crafting specially designed HTTP requests containing numerous duplicate headers, sending these requests in rapid succession to maximize memory consumption over time.
The operational impact of CVE-2008-4298 extends beyond simple resource exhaustion, creating significant availability risks for systems running vulnerable lighttpd versions. Remote attackers can effectively perform a denial of service attack by consuming system memory at an accelerating rate, potentially leading to complete service unavailability or system instability. The attack requires minimal sophistication as it only necessitates sending HTTP requests with duplicate headers, making it particularly dangerous for publicly accessible web servers. This vulnerability aligns with ATT&CK technique T1499.004, which describes resource exhaustion attacks targeting availability through memory consumption. The cumulative effect of this memory leak can cause the web server process to crash, restart repeatedly, or consume all available system memory, resulting in complete service disruption for legitimate users.
Mitigation strategies for this vulnerability require immediate patching of affected lighttpd installations to version 1.4.20 or later, where the memory leak has been addressed through proper memory management practices. System administrators should implement monitoring solutions to detect unusual memory consumption patterns that may indicate exploitation attempts, particularly focusing on memory usage trends of web server processes. Network-level protections such as rate limiting and request header validation can provide additional defense-in-depth measures, though these are secondary to the primary patching requirement. The fix implemented in version 1.4.20 demonstrates proper memory management practices, ensuring that header structures are correctly freed after processing, preventing the accumulation of unused memory blocks. Organizations should also consider implementing automated patch management processes to prevent similar vulnerabilities from persisting in their infrastructure, as this type of memory leak represents a fundamental flaw in resource handling that can have severe operational consequences.