CVE-2016-1376 in IOS XR
Summary
by MITRE
Cisco IOS XR 4.2.3, 4.3.0, 4.3.4, and 5.3.1 on ASR 9000 devices allows remote attackers to cause a denial of service (CRC and symbol errors, and interface flap) via crafted bit patterns in packets, aka Bug ID CSCuv78548.
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Analysis
by VulDB Data Team • 07/24/2022
Cisco IOS XR software running on ASR 9000 series devices contains a vulnerability that enables remote attackers to trigger denial of service conditions through carefully constructed packet bit patterns. This flaw affects multiple software versions including 4.2.3, 4.3.0, 4.3.4, and 5.3.1, representing a significant operational risk for network infrastructure. The vulnerability manifests as cyclic redundancy check crc errors and symbol errors that occur when malformed packets are processed by the device's network interfaces, leading to interface flapping behavior that disrupts network connectivity. The root cause lies in insufficient input validation within the packet processing pipeline where the system fails to properly handle malformed bit patterns that do not conform to expected network protocol standards. This vulnerability maps to CWE-129 Input Validation and CWE-770 Allocation of Resources Without Limits or Throttling, as the device does not properly limit resource consumption during packet processing. The impact extends beyond simple service disruption as the interface flapping can cause cascading failures across the network topology, affecting routing stability and potentially leading to extended outages. Attackers can exploit this vulnerability remotely without requiring authentication credentials, making it particularly dangerous in production environments where network availability is critical. The attack vector involves sending specifically crafted packets to interfaces that are configured to process traffic, which then causes the device to generate CRC and symbol errors, ultimately resulting in interface flap behavior that can persist until manual intervention or device reboot occurs. This vulnerability aligns with ATT&CK technique T1499.004 Network Denial of Service, as it specifically targets network infrastructure to cause service disruption through resource exhaustion and protocol handling failures. The operational impact includes potential network segmentation, routing instability, and extended service restoration times that can affect business continuity. Organizations should implement immediate mitigations including packet filtering rules to block suspicious traffic patterns, interface shutdown procedures for affected ports, and network monitoring to detect early signs of exploitation. The vulnerability demonstrates the importance of robust input validation in network operating systems and highlights the need for comprehensive testing of packet processing logic against malformed inputs. Network administrators should also consider implementing intrusion detection systems that can identify and alert on patterns consistent with this specific vulnerability. Regular software updates and patches from Cisco are essential for addressing this flaw, as the vulnerability represents a fundamental weakness in the IOS XR packet processing engine that requires vendor-level fixes to resolve completely.