CVE-2007-3948 in lighttpd
Summary
by MITRE
connections.c in lighttpd before 1.4.16 might accept more connections than the configured maximum, which allows remote attackers to cause a denial of service (failed assertion) via a large number of connection attempts.
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Analysis
by VulDB Data Team • 07/21/2021
The vulnerability identified as CVE-2007-3948 affects lighttpd versions prior to 1.4.16 and represents a critical resource management flaw that can lead to denial of service conditions. This issue resides within the connections.c module of the web server software, specifically in how the application handles connection limits. The vulnerability manifests when the server fails to properly enforce the maximum connection configuration parameters, allowing remote attackers to establish more concurrent connections than permitted by the system administrator's configuration settings. This behavior directly violates the principle of resource limiting that is fundamental to preventing system overloading and maintaining service availability.
The technical implementation of this flaw involves a failure in the connection tracking mechanism within lighttpd's core networking code. When the server receives a large volume of connection attempts, it does not properly validate against the configured maximum connection limits, leading to an accumulation of connections beyond the intended threshold. The vulnerability is particularly dangerous because it can trigger a failed assertion within the server's internal connection management code, causing the application to crash or terminate unexpectedly. This assertion failure represents a classic software error condition where the program encounters a state that violates its internal assumptions about connection counts and resource allocation. The flaw can be exploited through a simple flood of connection attempts without requiring any special privileges or complex attack vectors.
From an operational perspective, this vulnerability creates a significant risk of denial of service attacks against lighttpd servers. Attackers can systematically consume all available connection slots and then exceed the configured limits, causing the server to fail assertion checks and potentially crash entirely. The impact extends beyond simple service disruption to potentially compromising the entire web server infrastructure, especially in environments where lighttpd serves as a critical component of web application delivery. This vulnerability is particularly concerning for high-traffic websites and web applications that rely on connection limiting to prevent resource exhaustion attacks. The flaw can be leveraged in coordinated attacks that combine multiple connection attempts to overwhelm the server's ability to maintain proper connection state tracking.
The vulnerability aligns with CWE-129, which addresses improper validation of connection limits, and represents a direct violation of the principle of least privilege in resource management. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network denial of service attacks, and T1566.002, related to phishing attacks that could be used to initiate connection floods. The attack surface is particularly broad since it requires no authentication and can be executed from any network location. Mitigation strategies include immediate upgrade to lighttpd version 1.4.16 or later, where the connection limiting logic has been properly implemented and tested. Additionally, administrators should implement network-level rate limiting and connection tracking mechanisms as defense-in-depth measures. The fix addresses the underlying assertion failure by properly enforcing connection limits and implementing robust connection state management that prevents the accumulation of connections beyond configured thresholds.