CVE-2016-6421 in IOS XR
Summary
by MITRE
Cisco IOS XR 5.2.2 allows remote attackers to cause a denial of service (process restart) via a crafted OSPF Link State Advertisement (LSA) update, aka Bug ID CSCvb05643.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 04/29/2019
Cisco IOS XR 5.2.2 contains a critical vulnerability that enables remote attackers to trigger a denial of service condition through manipulation of OSPF Link State Advertisement updates. This vulnerability represents a fundamental flaw in the routing protocol processing mechanisms of the network operating system, specifically within the OSPF implementation that governs how routers exchange routing information. The issue manifests when the system receives a malformed or specially crafted LSA update that causes the routing process to restart unexpectedly, leading to temporary network disruption and potential service degradation across affected network segments.
The technical root cause of this vulnerability lies in insufficient input validation and error handling within the OSPF processing module of IOS XR. When the system encounters an improperly formatted LSA update, the parsing routine fails to properly validate the packet structure and contents, resulting in an unhandled exception that terminates the routing process. This behavior aligns with CWE-129, Input Validation and Representation, and CWE-248, Uncaught Exception, as the system does not adequately protect against malformed input data that could disrupt normal operations. The vulnerability specifically affects the OSPF Link State Advertisement processing within the routing daemon, where the system fails to implement robust bounds checking and data validation procedures.
The operational impact of this vulnerability extends beyond simple service interruption, as it can potentially compromise network stability and availability in production environments. Network administrators may observe unexpected router restarts or process failures that could affect multiple routing domains simultaneously, particularly in large-scale deployments where OSPF is extensively utilized. The remote exploitation capability means that attackers can trigger the vulnerability from outside the network perimeter without requiring local access or authentication credentials, making it particularly dangerous in environments where network segmentation is not properly implemented. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1499.004, Network Denial of Service, and T1562.001, Impair Command and Control, as it can be leveraged to disrupt network communications and potentially interfere with critical infrastructure operations.
Mitigation strategies for this vulnerability should prioritize immediate patch deployment through official Cisco security advisories and firmware updates that address the specific input validation flaws in the OSPF processing code. Network administrators should implement additional monitoring and alerting mechanisms to detect unusual routing process restarts or OSPF packet anomalies that could indicate exploitation attempts. Network segmentation and access control measures can help limit the potential impact by restricting unauthorized access to routing protocols and reducing the attack surface. Organizations should also consider implementing OSPF packet filtering and validation rules at network boundaries to prevent malformed LSA updates from reaching vulnerable systems, while maintaining detailed logging of routing protocol activities for forensic analysis and incident response purposes.