CVE-2009-5039 in IOS
Summary
by MITRE
Memory leak in the gk_circuit_info_do_in_acf function in the H.323 implementation in Cisco IOS before 15.0(1)XA allows remote attackers to cause a denial of service (memory consumption) via a large number of calls over a long duration, as demonstrated by InterZone Clear Token (IZCT) test traffic, aka Bug ID CSCsz72535.
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Analysis
by VulDB Data Team • 10/11/2021
The vulnerability identified as CVE-2009-5039 represents a critical memory management flaw within Cisco IOS operating systems that affects the H.323 protocol implementation. This issue specifically resides in the gk_circuit_info_do_in_acf function, which handles circuit information processing within the gateway component of Cisco's networking infrastructure. The vulnerability manifests as a memory leak that occurs during the processing of H.323 calls, particularly when subjected to sustained high-volume traffic patterns over extended periods. The flaw was particularly demonstrated through InterZone Clear Token (IZCT) test traffic, which simulates real-world conditions that would trigger the memory exhaustion scenario.
The technical nature of this vulnerability stems from improper memory deallocation within the H.323 gateway functionality, where allocated memory structures are not properly released when processing incoming calls. This memory leak occurs incrementally with each call processed, leading to progressive memory consumption until system resources are exhausted. The vulnerability affects Cisco IOS versions prior to 15.0(1)XA, indicating that this was a long-standing issue within the codebase that had not been properly addressed in earlier releases. The specific function gk_circuit_info_do_in_acf serves as the entry point where memory allocation occurs for circuit information processing, but lacks proper cleanup mechanisms when the call processing concludes.
Operationally, this vulnerability creates a significant denial of service condition that can severely impact network infrastructure reliability and availability. Remote attackers can exploit this flaw by initiating a large number of H.323 calls over an extended time period, effectively consuming all available memory resources on the affected Cisco device. The sustained nature of the attack makes it particularly dangerous as it can remain undetected while slowly degrading system performance until complete service disruption occurs. Network administrators may observe gradual performance degradation before the system becomes completely unresponsive, making early detection challenging. The InterZone Clear Token test traffic pattern used to demonstrate this vulnerability represents a realistic attack scenario that could occur in production environments with active H.323 gateways.
The impact of this vulnerability extends beyond simple service disruption to potentially compromise entire network communication infrastructures that rely on H.323 protocols for voice and video services. Organizations using Cisco devices for unified communications, video conferencing, or voice over IP services would be particularly vulnerable to this attack vector. The memory leak could affect not only the specific gateway device but also impact overall network performance by consuming critical system resources. This vulnerability aligns with CWE-401, which addresses improper deallocation of memory, and represents a classic example of resource exhaustion attacks that fall under the ATT&CK technique T1499.004 for network denial of service. The vulnerability also demonstrates characteristics of persistent attack patterns that can be classified under ATT&CK technique T1071.004 for application layer protocol usage.
Mitigation strategies for this vulnerability primarily involve applying the appropriate Cisco IOS software patches and updates that address the memory management issue within the H.323 implementation. Network administrators should prioritize upgrading affected devices to versions 15.0(1)XA or later, where the memory leak has been corrected. Additionally, implementing traffic monitoring and alerting systems can help detect unusual memory consumption patterns that may indicate exploitation attempts. Network segmentation and access control measures can limit the attack surface by restricting unauthorized access to H.323 gateway functions. Organizations should also consider implementing call rate limiting and monitoring mechanisms to detect and prevent sustained high-volume call patterns that could trigger the memory leak. The vulnerability highlights the importance of proper memory management practices in network infrastructure software and underscores the need for regular security patching and vulnerability management programs.