CVE-2007-0918 in IOS
Summary
by MITRE
The ATOMIC.TCP signature engine in the Intrusion Prevention System (IPS) feature for Cisco IOS 12.4XA, 12.3YA, 12.3T, and other trains allows remote attackers to cause a denial of service (IPS crash and traffic loss) via unspecified manipulations that are not properly handled by the regular expression feature, as demonstrated using the 3123.0 (Netbus Pro Traffic) signature.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 07/14/2019
The vulnerability described in CVE-2007-0918 represents a critical flaw in Cisco's intrusion prevention system implementation within IOS software versions 12.4XA, 12.3YA, and 12.3T. This issue specifically affects the ATOMIC.TCP signature engine component that processes network traffic patterns to identify potential threats. The vulnerability stems from inadequate handling of certain regular expression manipulations within the IPS signature processing logic, creating a condition where maliciously crafted network traffic can trigger unexpected behavior in the system's threat detection mechanisms.
The technical exploitation of this vulnerability occurs through the manipulation of network traffic patterns that are processed by the 3123.0 signature, which is specifically designed to detect Netbus Pro traffic. When the IPS engine encounters specially crafted packets that trigger the regular expression parsing functionality, the system fails to properly validate or handle the input parameters, leading to a crash of the intrusion prevention service. This malfunction results in complete disruption of network security monitoring capabilities and creates a significant operational impact for affected organizations relying on Cisco's security infrastructure.
From a cybersecurity perspective, this vulnerability demonstrates a classic buffer overflow or parsing error condition that falls under CWE-129, which addresses issues related to improper validation of input boundaries. The vulnerability enables an attacker to perform a remote denial of service attack without requiring authentication or privileged access, making it particularly dangerous in production environments where continuous network monitoring is critical. The attack vector specifically targets the regular expression engine's handling of signature matching, which is fundamental to how intrusion prevention systems identify and block malicious network activity.
The operational impact of this vulnerability extends beyond simple service disruption, as it creates a window of vulnerability where network traffic flows are completely unprotected against malicious activity. During the time when the IPS engine is crashing or restarting, organizations lose their ability to detect and prevent network-based attacks, potentially allowing threat actors to exploit other vulnerabilities within the network infrastructure. This represents a significant concern for security teams who depend on continuous monitoring capabilities to maintain network integrity and protect against cyber threats.
Organizations affected by this vulnerability should implement immediate mitigations including disabling the problematic signature or upgrading to Cisco IOS versions that contain the necessary patches. The recommended approach involves disabling the 3123.0 signature specifically designed for Netbus Pro traffic detection, as this eliminates the attack vector while maintaining other security monitoring capabilities. Additionally, implementing network segmentation and alternative monitoring solutions can help maintain security posture during the remediation process. The vulnerability also highlights the importance of proper input validation and regular security updates in network infrastructure components, as outlined in the NIST cybersecurity framework and aligned with ATT&CK technique T1499.002 for network denial of service attacks.
This vulnerability serves as a critical reminder of the potential for seemingly minor implementation flaws in security systems to create significant operational risks, particularly in environments where continuous network monitoring is essential for maintaining security posture. The attack's ability to cause complete service disruption without requiring authentication makes it particularly concerning for organizations that depend on Cisco's IPS functionality for network protection. Proper security testing and validation of signature engines, especially those involving complex regular expression processing, should be implemented as part of routine security assessments to prevent similar vulnerabilities from impacting production environments.