CVE-2008-1531 in lighttpd
Summary
by MITRE
The connection_state_machine function (connections.c) in lighttpd 1.4.19 and earlier, and 1.5.x before 1.5.0, allows remote attackers to cause a denial of service (active SSL connection loss) by triggering an SSL error, such as disconnecting before a download has finished, which causes all active SSL connections to be lost.
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Analysis
by VulDB Data Team • 07/31/2021
The vulnerability identified as CVE-2008-1531 represents a critical denial of service flaw within the lighttpd web server software affecting versions 1.4.19 and earlier, as well as 1.5.x versions prior to 1.5.0. This issue stems from improper handling of SSL connection states within the server's core networking logic, specifically within the connection_state_machine function located in the connections.c file. The flaw demonstrates how a seemingly routine network interruption can be exploited to trigger catastrophic system behavior, affecting all active SSL connections simultaneously.
The technical implementation of this vulnerability exploits a race condition and state management error in the SSL connection handling mechanism. When a remote attacker intentionally triggers an SSL error through premature disconnection or network interruption during an active SSL session, the connection_state_machine function fails to properly manage the transition between connection states. This improper state handling causes the server to lose track of active SSL connections, resulting in the complete breakdown of all ongoing SSL sessions. The vulnerability operates at the protocol level where the server's internal state machine becomes corrupted, leading to a cascading failure that affects the entire SSL connection pool rather than individual sessions.
From an operational perspective, this vulnerability presents a severe threat to web services relying on SSL encryption, as it can be exploited to disrupt service availability for all users simultaneously. The impact extends beyond simple service interruption to potentially affecting user trust and business continuity, particularly in environments where SSL connections are critical for secure data transmission. Attackers can leverage this weakness to cause widespread disruption without requiring elevated privileges or complex exploitation techniques, making it particularly dangerous in production environments where service availability is paramount.
The vulnerability maps directly to CWE-400, which addresses "Uncontrolled Resource Consumption," and aligns with ATT&CK technique T1499.004 for "Network Denial of Service" within the adversary tactics framework. Organizations using affected lighttpd versions should implement immediate mitigations including upgrading to patched versions 1.4.20 or 1.5.0 and later, implementing network-level protections such as rate limiting and connection monitoring, and establishing proper SSL connection handling procedures. Additionally, system administrators should consider implementing intrusion detection systems to monitor for abnormal connection patterns and ensure proper resource allocation to prevent exploitation of this state management flaw.