CVE-2017-6770 in NX-OS
Summary
by MITRE
Cisco IOS 12.0 through 15.6, Adaptive Security Appliance (ASA) Software 7.0.1 through 9.7.1.2, NX-OS 4.0 through 12.0, and IOS XE 3.6 through 3.18 are affected by a vulnerability involving the Open Shortest Path First (OSPF) Routing Protocol Link State Advertisement (LSA) database. This vulnerability could allow an unauthenticated, remote attacker to take full control of the OSPF Autonomous System (AS) domain routing table, allowing the attacker to intercept or black-hole traffic. The attacker could exploit this vulnerability by injecting crafted OSPF packets. Successful exploitation could cause the targeted router to flush its routing table and propagate the crafted OSPF LSA type 1 update throughout the OSPF AS domain. To exploit this vulnerability, an attacker must accurately determine certain parameters within the LSA database on the target router. This vulnerability can only be triggered by sending crafted unicast or multicast OSPF LSA type 1 packets. No other LSA type packets can trigger this vulnerability. OSPFv3 is not affected by this vulnerability. Fabric Shortest Path First (FSPF) protocol is not affected by this vulnerability. Cisco Bug IDs: CSCva74756, CSCve47393, CSCve47401.
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Analysis
by VulDB Data Team • 01/06/2021
This vulnerability resides within the Open Shortest Path First routing protocol implementation across multiple Cisco networking platforms including IOS, ASA, and NX-OS software versions. The flaw specifically affects OSPF LSA type 1 database processing where an unauthenticated remote attacker can manipulate the routing table through crafted OSPF packets. The vulnerability represents a critical security issue as it allows complete takeover of the OSPF autonomous system domain routing table, enabling sophisticated traffic interception or black-holing attacks. The technical implementation involves the router's handling of Link State Advertisement updates where the malformed packet processing creates a condition that allows arbitrary routing table manipulation.
The core technical flaw manifests when the targeted router processes crafted OSPF LSA type 1 packets that contain manipulated parameters within the LSA database structure. This vulnerability operates under CWE-121, which describes buffer overflow conditions, and specifically relates to improper handling of input data within routing protocol implementations. The exploitation requires precise parameter manipulation within the LSA database fields that control routing table updates, making it a complex attack vector that demands detailed knowledge of the OSPF protocol internals. The vulnerability cannot be triggered through any other LSA type packets, limiting the attack surface but making the specific exploitation technique more targeted and sophisticated.
The operational impact of this vulnerability extends far beyond simple network disruption, as it enables complete routing table compromise across an entire OSPF autonomous system domain. An attacker who successfully exploits this vulnerability can redirect all traffic through malicious paths, effectively creating a man-in-the-middle position for traffic interception or completely blocking traffic through black-hole routing. This capability directly maps to ATT&CK technique T1072, which covers protocol manipulation and T1566, which involves credential harvesting through network manipulation. The vulnerability affects multiple Cisco platforms including IOS versions 12.0 through 15.6, ASA Software 7.0.1 through 9.7.1.2, NX-OS 4.0 through 12.0, and IOS XE 3.6 through 3.18, representing a significant attack surface across enterprise networking infrastructure.
Mitigation strategies should focus on implementing proper OSPF authentication mechanisms including MD5 authentication or SHA-256 authentication for OSPF routing updates, which would prevent the injection of unauthorized LSA packets. Network segmentation and access control lists should be deployed to limit OSPF packet transmission to trusted sources only, implementing the principle of least privilege for routing protocol communications. Cisco recommends upgrading to software versions that contain patches for this vulnerability, with specific attention to the bug IDs CSCva74756, CSCve47393, and CSCve47401 which contain the relevant fixes. Network administrators should also implement monitoring for unusual OSPF packet patterns and establish network segmentation to limit the potential impact of successful exploitation, as the vulnerability allows propagation throughout the entire OSPF domain. Additionally, implementing network access control and ensuring that only authorized devices can participate in OSPF routing protocols will significantly reduce the attack surface for this specific vulnerability.