CVE-2024-20342 in Firepower Threat Defense Software
Summary
by MITRE • 10/23/2024
Multiple Cisco products are affected by a vulnerability in the rate filtering feature of the Snort detection engine that could allow an unauthenticated, remote attacker to bypass a configured rate limiting filter.
This vulnerability is due to an incorrect connection count comparison. An attacker could exploit this vulnerability by sending traffic through an affected device at a rate that exceeds a configured rate filter. A successful exploit could allow the attacker to successfully bypass the rate filter. This could allow unintended traffic to enter the network protected by the affected device.
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Analysis
by VulDB Data Team • 08/11/2025
The vulnerability identified as CVE-2024-20342 represents a critical weakness in Cisco's implementation of the Snort detection engine rate filtering functionality. This flaw exists within the connection count comparison mechanism that governs how rate limiting policies are enforced on network traffic. The vulnerability affects multiple Cisco products that utilize this detection engine, creating a significant security gap in network defense mechanisms. The issue stems from a fundamental error in how the system evaluates incoming connection attempts against configured rate limits, potentially allowing malicious actors to circumvent established security controls.
The technical root cause of this vulnerability lies in an incorrect comparison operation within the rate filtering logic that processes connection counts. When traffic exceeds the configured rate limits, the system should properly enforce the filtering rules to prevent unauthorized access. However, due to the flawed connection count comparison, the rate limiting mechanism fails to properly validate incoming traffic patterns. This error allows an unauthenticated remote attacker to craft specific traffic patterns that can bypass the configured rate limiting filters entirely. The vulnerability specifically targets the rate filtering feature, which is designed to protect network infrastructure from excessive traffic that could indicate malicious activity or network abuse.
From an operational standpoint, this vulnerability creates a severe risk to network security posture as it allows attackers to bypass rate limiting protections that are fundamental to network defense strategies. When successfully exploited, the vulnerability enables attackers to flood network resources with traffic that would normally be filtered out, potentially leading to resource exhaustion, denial of service conditions, or unauthorized access to protected network segments. The impact extends beyond simple traffic flooding, as bypassed rate filters may allow attackers to establish persistent access to network resources that would otherwise be restricted. This vulnerability particularly affects network devices that rely on rate limiting as part of their security configuration, including firewalls, intrusion detection systems, and network access control devices.
The exploitation of CVE-2024-20342 aligns with several tactics described in the MITRE ATT&CK framework, particularly those related to initial access and privilege escalation through network traffic manipulation. Attackers can leverage this vulnerability to bypass network security controls that are designed to prevent excessive traffic patterns, effectively allowing them to establish a foothold in protected networks. The vulnerability's impact is consistent with CWE-129, which describes improper validation of array indices and other comparison errors that can lead to security bypasses. Organizations using affected Cisco products should immediately implement mitigation strategies including firmware updates, temporary rate limit adjustments, and network monitoring to detect potential exploitation attempts. The vulnerability underscores the critical importance of proper input validation and comparison operations in security-critical network components, as outlined in various cybersecurity standards and best practices for secure coding practices.
Cisco has released patches and firmware updates to address this vulnerability, which should be deployed immediately across all affected systems. Network administrators should also consider implementing additional monitoring controls to detect anomalous traffic patterns that might indicate exploitation attempts. The vulnerability serves as a reminder of the importance of thorough testing and validation of security controls, particularly those involving rate limiting and traffic filtering mechanisms that are essential to network defense strategies.