CVE-2012-4534 in Tomcat
Summary
by MITRE
org/apache/tomcat/util/net/NioEndpoint.java in Apache Tomcat 6.x before 6.0.36 and 7.x before 7.0.28, when the NIO connector is used in conjunction with sendfile and HTTPS, allows remote attackers to cause a denial of service (infinite loop) by terminating the connection during the reading of a response.
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Analysis
by VulDB Data Team • 04/19/2021
The vulnerability identified as CVE-2012-4534 represents a critical denial of service flaw within Apache Tomcat's networking implementation that specifically affects versions prior to 6.0.36 and 7.0.28. This issue manifests when the NIO (Non-blocking I/O) connector is configured to work alongside sendfile functionality and HTTPS protocol, creating a scenario where remote attackers can exploit a design flaw that leads to infinite loop conditions within the server's response handling mechanism. The vulnerability resides in the org/apache/tomcat/util/net/NioEndpoint.java file, which governs how Tomcat processes network connections using the NIO architecture.
The technical root cause of this vulnerability stems from improper handling of connection termination events during the response reading phase when sendfile operations are active. When an attacker terminates a connection while Tomcat is in the process of reading and sending a response through the NIO connector with sendfile enabled over HTTPS, the system enters an infinite loop condition. This occurs because the connection state management fails to properly detect and handle the abrupt termination, causing the server to repeatedly attempt to process the same incomplete response data. The flaw is particularly insidious because it can be triggered remotely without requiring authentication or specialized privileges, making it a significant threat to server availability.
The operational impact of this vulnerability extends beyond simple service disruption, as it can effectively render affected Tomcat servers unusable for extended periods. Attackers can repeatedly trigger this condition to maintain a persistent denial of service state, consuming server resources and potentially causing system instability. The infinite loop consumes CPU cycles continuously while the server remains unable to process legitimate requests, effectively creating a resource exhaustion scenario that impacts all users of the affected service. This vulnerability particularly affects web applications that rely heavily on HTTPS and file serving capabilities, which are common in enterprise environments and web applications requiring secure file transfers.
Organizations affected by this vulnerability should immediately implement the recommended patches and updates to their Tomcat installations, ensuring that all systems are upgraded to versions 6.0.36 or later for the 6.x series, and 7.0.28 or later for the 7.x series. Additionally, administrators should consider implementing network-level mitigations such as connection rate limiting and monitoring for unusual connection termination patterns. The vulnerability aligns with CWE-835, which addresses the issue of infinite loops in software implementations, and can be categorized under ATT&CK technique T1499.100, specifically targeting network denial of service through resource exhaustion. Security teams should also review their current monitoring solutions to detect potential exploitation attempts and implement proper logging of connection termination events to identify anomalous patterns that may indicate an active attack.