CVE-2011-4905 in ActiveMQ
Summary
by MITRE
Apache ActiveMQ before 5.6.0 allows remote attackers to cause a denial of service (file-descriptor exhaustion and broker crash or hang) by sending many openwire failover:tcp:// connection requests.
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Analysis
by VulDB Data Team • 02/13/2019
Apache ActiveMQ version 5.6.0 and earlier contains a critical vulnerability that enables remote attackers to execute denial of service attacks through strategic manipulation of connection requests. This vulnerability specifically targets the OpenWire protocol implementation within the messaging broker, where malicious actors can exploit the system's connection handling mechanisms to exhaust available file descriptors. The flaw resides in how ActiveMQ processes failover connection requests, creating a scenario where multiple concurrent connection attempts can rapidly deplete the system's available file descriptor limits. This behavior aligns with CWE-400, which categorizes unchecked resource consumption as a significant security weakness affecting system availability. The vulnerability operates by sending numerous failover:tcp:// connection requests that, when processed by the broker, create a cascade of file descriptor allocations without proper cleanup or rate limiting mechanisms.
The technical exploitation of this vulnerability demonstrates a fundamental flaw in resource management and connection lifecycle handling within the ActiveMQ broker. When multiple failover connection requests are simultaneously processed, each request consumes a file descriptor to maintain the connection state and associated network resources. The broker's failure to properly implement connection throttling or resource cleanup protocols means that these file descriptors remain allocated even after the connection attempts are completed or fail. This creates a gradual but systematic depletion of available system resources, ultimately leading to the broker becoming unresponsive or crashing entirely. The attack vector specifically leverages the OpenWire protocol's failover mechanism, which is designed to provide high availability by allowing clients to reconnect to alternative broker endpoints when primary connections fail. However, this same mechanism becomes exploitable when abused through excessive connection attempts, as the broker cannot distinguish between legitimate connection failures and malicious resource exhaustion attempts.
The operational impact of CVE-2011-4905 extends beyond simple service disruption to potentially compromise the entire messaging infrastructure that relies on ActiveMQ. When the broker crashes or becomes unresponsive due to file descriptor exhaustion, all dependent applications and services that depend on message queuing functionality experience cascading failures. This vulnerability affects organizations using ActiveMQ for critical business processes, including financial transactions, healthcare data exchange, and enterprise application integration. The attack requires minimal sophistication and can be executed from any network location, making it particularly dangerous for systems exposed to untrusted networks. From an adversary perspective, this vulnerability maps directly to ATT&CK technique T1499.004, which covers network denial of service attacks targeting system resources. The vulnerability's impact is amplified in environments where ActiveMQ serves as a central messaging hub, as the disruption affects not just the broker itself but potentially the entire distributed application ecosystem that depends on reliable message queuing services.
Organizations should implement immediate mitigations including upgrading to ActiveMQ version 5.6.0 or later, which includes fixes for the file descriptor management issues. System administrators should also configure connection limits and implement rate limiting policies to prevent excessive concurrent connection attempts from overwhelming the broker. Network-level controls such as firewall rules and connection tracking mechanisms can help limit the number of simultaneous connection requests from individual sources. Additionally, monitoring should be implemented to detect unusual connection patterns and file descriptor usage spikes that may indicate exploitation attempts. The vulnerability highlights the importance of proper resource management and connection lifecycle handling in enterprise messaging systems, as demonstrated by the CWE-400 classification for unchecked resource consumption. Organizations should also consider implementing intrusion detection systems that can identify and alert on abnormal connection patterns characteristic of this attack vector. Regular security assessments of messaging infrastructure and adherence to security best practices for resource management will help prevent similar vulnerabilities from being exploited in the future, particularly in environments where legacy systems may be exposed to external threats without proper patch management protocols.