CVE-2014-3396 in IOS XR
Summary
by MITRE
Cisco IOS XR on ASR 9000 devices does not properly use compression for port-range and address-range encoding, which allows remote attackers to bypass intended Typhoon line-card ACL restrictions via transit traffic, aka Bug ID CSCup30133.
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Analysis
by VulDB Data Team • 06/08/2017
The vulnerability identified as CVE-2014-3396 affects Cisco IOS XR software running on ASR 9000 devices, specifically impacting the handling of port-range and address-range encoding within the Typhoon line-card ACL implementation. This flaw represents a critical security weakness that undermines the intended network access control mechanisms designed to protect against unauthorized traffic flows. The issue stems from improper compression techniques used during the processing of network traffic patterns, creating a bypass mechanism that allows malicious actors to circumvent established security policies.
The technical root cause of this vulnerability lies in the insufficient compression algorithms employed for encoding port ranges and address ranges within the ACL processing pipeline. When the system processes network traffic that matches specific port or address patterns, the compression mechanism fails to properly account for all possible variations in the encoded data structures. This compression failure creates predictable gaps in the access control enforcement, enabling attackers to craft transit traffic that appears to comply with ACL restrictions while actually exploiting the compression artifacts to bypass these controls. The vulnerability specifically affects the Typhoon line-card architecture which is integral to the ASR 9000 platform's packet processing capabilities.
The operational impact of this vulnerability is significant as it allows remote attackers to gain unauthorized access to network resources that should be protected by ACL restrictions. Attackers can exploit this weakness to bypass network segmentation controls, potentially gaining access to sensitive network zones or systems that are supposed to be isolated from general traffic flows. The remote nature of the attack means that adversaries do not require physical access to the network infrastructure, making this vulnerability particularly dangerous in enterprise and service provider environments where network security is paramount. This flaw essentially creates a backdoor mechanism that can be leveraged to establish persistent access or conduct advanced persistent threat activities.
Organizations should implement immediate mitigations including applying the relevant Cisco security patches and updates to address the compression handling issue in the IOS XR software. Network administrators should also consider implementing additional monitoring and detection mechanisms to identify anomalous traffic patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-129, which addresses improper handling of input boundaries, and relates to ATT&CK technique T1071.004 for application layer protocol: DNS, as attackers might leverage this weakness to establish command and control communications. Organizations should also review their existing ACL configurations to ensure proper enforcement of network access controls and consider implementing network segmentation strategies that reduce the potential impact of such vulnerabilities. The mitigation strategy should include comprehensive testing of the patched software to ensure that the compression algorithms function correctly without introducing new stability issues in the network infrastructure.