CVE-2022-20823 in NX-OS
Summary
by MITRE • 08/25/2022
A vulnerability in the OSPF version 3 (OSPFv3) feature of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to incomplete input validation of specific OSPFv3 packets. An attacker could exploit this vulnerability by sending a malicious OSPFv3 link-state advertisement (LSA) to an affected device. A successful exploit could allow the attacker to cause the OSPFv3 process to crash and restart multiple times, causing the affected device to reload and resulting in a DoS condition. Note: The OSPFv3 feature is disabled by default. To exploit this vulnerability, an attacker must be able to establish a full OSPFv3 neighbor state with an affected device. For more information about exploitation conditions, see the Details section of this advisory.
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Analysis
by VulDB Data Team • 10/01/2022
The vulnerability identified as CVE-2022-20823 represents a critical denial of service weakness within Cisco NX-OS Software's OSPF version 3 implementation. This flaw specifically targets the OSPFv3 routing protocol functionality that operates within enterprise network infrastructures, where the protocol facilitates dynamic routing updates between network devices. The vulnerability stems from inadequate input validation mechanisms within the software's processing of OSPFv3 link-state advertisements, creating an exploitable condition that can be leveraged by remote attackers without requiring authentication credentials. The affected software components reside within the network operating system's routing protocol stack, where OSPFv3 packets are parsed and processed to maintain network topology information across the routed domain.
The technical exploitation mechanism involves crafting malicious OSPFv3 link-state advertisements that contain malformed or unexpected data structures which the software fails to properly validate before processing. When an affected device receives such malicious packets, the incomplete input validation causes the OSPFv3 process to encounter an unhandled exception or memory corruption condition. This leads to a cascading failure where the OSPFv3 routing process crashes and attempts to restart automatically, creating a loop of process failures that ultimately results in a complete device reload. The vulnerability requires an attacker to establish a full OSPFv3 neighbor relationship with the target device, meaning network access must be available to send the malicious packets through the network infrastructure. This prerequisite significantly limits the attack surface but does not eliminate the risk for networks where OSPFv3 is enabled and accessible to potential attackers.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network stability and availability. When the OSPFv3 process repeatedly crashes and restarts, it causes routing table inconsistencies and network convergence issues that can affect multiple network segments. The automatic device reload triggered by the vulnerability can result in extended network downtime as the system reinitializes all routing processes and potentially disrupts ongoing network communications. Network administrators may experience challenges in troubleshooting since the DoS condition can occur without clear audit trail indicators, making it difficult to distinguish between legitimate routing protocol issues and malicious exploitation. The vulnerability's default-disabled state provides some protection, but organizations that have explicitly enabled OSPFv3 for network routing purposes face significant risk exposure.
Organizations should implement immediate mitigations to address this vulnerability, beginning with ensuring OSPFv3 remains disabled unless absolutely required for network operations. Network segmentation strategies should be employed to limit OSPFv3 communication to trusted network segments only, reducing the potential attack surface. Access control lists and firewall rules should be configured to restrict OSPFv3 traffic to authorized network devices and prevent unauthorized access to OSPFv3 neighbor establishment. Cisco recommends applying the latest software patches and updates that address the input validation deficiencies in the OSPFv3 implementation, which typically involve enhanced packet validation routines and improved error handling mechanisms. Network monitoring should be enhanced to detect unusual OSPFv3 process restart patterns and potential malicious packet injection attempts. The vulnerability aligns with CWE-20 input validation weakness and could be categorized under ATT&CK technique T1499 for network disruption and T1566 for credential harvesting, though the specific DoS nature makes it primarily a network service availability attack vector.