CVE-2010-0295 in lighttpd
Summary
by MITRE
lighttpd before 1.4.26, and 1.5.x, allocates a buffer for each read operation that occurs for a request, which allows remote attackers to cause a denial of service (memory consumption) by breaking a request into small pieces that are sent at a slow rate.
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Analysis
by VulDB Data Team • 04/30/2026
The vulnerability identified as CVE-2010-0295 affects lighttpd web servers version 1.4.25 and earlier, as well as version 1.5.x series, presenting a significant denial of service weakness that can be exploited remotely. This flaw resides in the server's handling of HTTP request processing where the software allocates memory buffers on a per-read-operation basis rather than utilizing a more efficient buffering strategy. The vulnerability is classified under CWE-400 as an Uncontrolled Resource Consumption issue, which represents a classic resource exhaustion attack vector. The attack mechanism leverages the server's inefficient memory allocation pattern by fragmenting HTTP requests into numerous small pieces that are transmitted at deliberately slow intervals, causing the web server to continuously allocate memory buffers without proper cleanup or reuse mechanisms.
The technical implementation of this vulnerability exploits a fundamental flaw in lighttpd's request parsing architecture where each individual read operation triggers a new buffer allocation regardless of the overall request size or processing state. This design choice leads to exponential memory consumption as attackers can maintain multiple concurrent connections while sending minimal data chunks over extended periods, effectively starving the server's memory resources. The operational impact is particularly severe because the vulnerability can be executed with minimal network bandwidth requirements, making it particularly dangerous in environments where server resources are constrained or where attackers have limited network capacity. The attack pattern follows typical resource exhaustion techniques described in the ATT&CK framework under the T1499.004 sub-technique for Resource Exhaustion, where adversaries consume system resources to prevent legitimate use of services.
From a security perspective, this vulnerability demonstrates poor memory management practices in web server implementations and highlights the importance of proper buffer handling and resource allocation strategies. The flaw essentially allows an attacker to consume memory at a rate proportional to the number of concurrent connections multiplied by the frequency of read operations, creating a scenario where legitimate users may be unable to access services due to resource exhaustion. The vulnerability affects both the 1.4.x and 1.5.x release lines, indicating a systemic issue within the server's architecture that required a complete version upgrade to resolve. Organizations running affected versions should immediately implement mitigations such as connection rate limiting, implementing proper timeouts, and restricting the number of concurrent connections to reduce the attack surface. The fix included in lighttpd version 1.4.26 introduced more efficient buffering mechanisms and proper memory management practices that prevent the accumulation of unused buffers during slow request processing. This vulnerability also underscores the critical importance of regular security updates and the potential for seemingly minor architectural decisions to create significant security risks in network services.