CVE-2024-20330 in Firepower Threat Defense Software
Summary
by MITRE • 10/23/2024
A vulnerability in the Snort 2 and Snort 3 TCP and UDP detection engine of Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 2100 Series Appliances could allow an unauthenticated, remote attacker to cause memory corruption, which could cause the Snort detection engine to restart unexpectedly.
This vulnerability is due to improper memory management when the Snort detection engine processes specific TCP or UDP packets. An attacker could exploit this vulnerability by sending crafted TCP or UDP packets through a device that is inspecting traffic using the Snort detection engine. A successful exploit could allow the attacker to restart the Snort detection engine repeatedly, which could cause a denial of service (DoS) condition. The DoS condition impacts only the traffic through the device that is examined by the Snort detection engine. The device can still be managed over the network. Note: Once a memory block is corrupted, it cannot be cleared until the Cisco Firepower 2100 Series Appliance is manually reloaded. This means that the Snort detection engine could crash repeatedly, causing traffic that is processed by the Snort detection engine to be dropped until the device is manually reloaded.
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Analysis
by VulDB Data Team • 08/06/2025
The vulnerability identified as CVE-2024-20330 represents a critical memory management flaw within the Snort detection engines of Cisco Firepower Threat Defense software operating on Cisco Firepower 2100 Series appliances. This issue affects both Snort 2 and Snort 3 implementations, creating a significant attack surface for unauthenticated remote adversaries who can exploit the weakness through carefully crafted TCP or UDP packet transmissions. The vulnerability stems from inadequate handling of memory allocation and deallocation processes during packet inspection, specifically when processing certain network traffic patterns that trigger memory corruption conditions within the detection engine's operational framework.
The technical exploitation of this vulnerability occurs through the manipulation of TCP or UDP packet structures that cause the Snort detection engine to improperly manage memory resources. When these malformed packets are processed, the engine encounters memory corruption that leads to unexpected restarts of the detection service. This memory management failure operates at the core of the detection engine's packet processing logic, where insufficient bounds checking or improper memory deallocation routines create opportunities for attackers to repeatedly trigger the same corruption conditions. The flaw manifests as a cascading restart condition that can be perpetuated through continuous packet injection, effectively creating a persistent denial of service scenario that specifically targets the traffic inspection capabilities of the appliance.
The operational impact of this vulnerability extends beyond simple service disruption, as the memory corruption creates a persistent state that requires manual intervention to resolve. Once memory blocks become corrupted, they remain in a compromised state until the appliance undergoes a complete manual reload, meaning that the system cannot recover from the corruption through normal restart procedures. This creates a particularly challenging scenario for network defenders, as the DoS condition affects only traffic processed by the Snort detection engine while maintaining the appliance's management capabilities over the network. The targeted nature of the attack means that legitimate traffic flowing through the device's inspection paths becomes disrupted, potentially creating gaps in network security monitoring and threat detection capabilities that could be exploited by more sophisticated attackers.
Organizations utilizing Cisco Firepower 2100 Series appliances should prioritize immediate remediation through official Cisco software updates and patches that address the memory management deficiencies in the Snort detection engines. The vulnerability aligns with CWE-129, which describes improper validation of array index values, and represents a specific implementation weakness in memory handling routines that could be classified under ATT&CK technique T1499.004 for network denial of service attacks. Network security teams should implement monitoring protocols to detect unusual restart patterns in the Snort detection engine and establish procedures for manual device reloading when corruption conditions are identified. Additionally, implementing network segmentation and traffic filtering mechanisms can help limit the attack surface and reduce the potential impact of exploitation attempts, while maintaining awareness of the specific packet patterns that could trigger the vulnerability during ongoing network operations.