CVE-2012-5568 in Tomcat
Summary
by MITRE
Apache Tomcat through 7.0.x allows remote attackers to cause a denial of service (daemon outage) via partial HTTP requests, as demonstrated by Slowloris.
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Analysis
by VulDB Data Team • 12/20/2021
The vulnerability identified as CVE-2012-5568 represents a significant denial of service weakness in Apache Tomcat versions up to 7.0.x that enables remote attackers to disrupt service availability through carefully crafted partial HTTP requests. This flaw specifically exploits the server's handling of incomplete HTTP requests, creating a condition where the daemon becomes unresponsive and effectively unavailable to legitimate users. The vulnerability gained notoriety through its exploitation in the Slowloris attack pattern, which demonstrates how attackers can maintain persistent connections to the server while sending incomplete requests that consume available connections and resources. This type of attack directly targets the server's resource management capabilities and connection handling mechanisms, making it particularly dangerous for web applications that rely on Tomcat as their application server.
The technical root cause of this vulnerability lies in Tomcat's HTTP connector implementation, which fails to properly terminate or time out connections when receiving incomplete HTTP requests. When an attacker sends partial HTTP requests that never complete, the server maintains these connections in a waiting state, gradually consuming available connection slots and thread resources. This behavior creates a resource exhaustion scenario where legitimate requests cannot be processed because all available connection handlers are occupied by the incomplete requests. The vulnerability operates at the protocol level, specifically within the HTTP request parsing and connection management components, where the server lacks adequate timeout mechanisms or connection limiting features to prevent such resource depletion attacks. According to CWE standards, this represents a weakness categorized under CWE-400, which deals with resource exhaustion vulnerabilities, and more specifically aligns with CWE-770, which addresses allocation of resources without limits or throttling.
The operational impact of CVE-2012-5568 extends beyond simple service disruption to potentially compromise the entire availability of web applications hosted on affected Tomcat servers. Attackers can maintain persistent connections for extended periods, effectively starving the server of resources needed to serve legitimate users, leading to cascading failures that may affect business operations and customer experience. This vulnerability particularly affects high-traffic applications where connection limits are already near capacity, as the attack can quickly overwhelm available resources and cause complete service outage. The attack vector is relatively simple to execute, requiring minimal technical expertise, which makes it a popular choice for attackers seeking to disrupt services. Organizations running Tomcat servers without proper mitigation measures face significant risk of prolonged outages that can result in financial losses, reputation damage, and potential compliance violations.
Mitigation strategies for this vulnerability focus on implementing connection timeout mechanisms, limiting concurrent connections, and configuring proper resource management parameters within the Tomcat server configuration. Administrators should configure appropriate connection timeouts in the server.xml file to ensure that incomplete requests are automatically terminated after a reasonable time period. Implementing connection limits through the maxConnections parameter helps prevent resource exhaustion by restricting the total number of concurrent connections. Network-level protections such as firewalls and load balancers can also be configured to detect and block suspicious connection patterns that match Slowloris attack characteristics. Additionally, upgrading to patched versions of Tomcat 7.0.x that include fixes for this vulnerability represents the most effective long-term solution. Security teams should also implement monitoring and alerting mechanisms to detect unusual connection patterns that may indicate an ongoing attack, enabling rapid response to prevent service disruption. The ATT&CK framework categorizes this vulnerability under the T1499.004 technique for network denial of service, highlighting the importance of proper resource management and connection handling in defensive security strategies.