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October 2023: Critical Advisory on Cisco N3K/N9K Health DOS Vulnerability (CVE-2025-20111)
Executive Summary
A newly identified vulnerability, CVE-2025-20111, has been discovered in Cisco Nexus 3000 and Nexus 9000 Series Switches. This vulnerability, with a CVSS score of 7.4, is critical as it allows an unauthenticated, adjacent attacker to potentially cause a denial of service (DoS) through the unexpected reloading of the device by manipulating specific Ethernet frames. This document examines the technical details, potential exploitation, and strategies for mitigation.
Technical Information
The Cisco N3K/N9K Health DOS vulnerability (CVE-2025-20111) is characterized by its presence in the health monitoring diagnostics of the Cisco Nexus 3000 and Nexus 9000 Series Switches operating in standalone NX-OS mode. This vulnerability is identified by CWE-1220: Insufficient Granularity of Access Control. With an adjacent attack vector, no privileges required, and no user interaction necessary, this vulnerability has a high availability impact.
The vulnerability originates due to improper handling of specific Ethernet frames, which can be exploited by an attacker to reload the device, resulting in a DoS condition. It is significant due to the potential for network disruptions, particularly in environments relying on these switches for critical operations.
Affected devices include Nexus 3100, 3200, 3400, 3600, 9200, 9300, and 9400 Series Switches, provided they are running a vulnerable version of Cisco NX-OS Software. This vulnerability changes the scope of the device's operation, making its impact substantial.
Exploitation in the Wild
As of now, there are no documented cases of active exploitation in the wild. Attackers could potentially exploit this vulnerability by sending crafted Ethernet frames at a sustained rate to the affected device, triggering a device reload and causing a denial of service. Indicators of Compromise (IoCs) include the failure of the L2ACLRedirect or RewriteEngineLoopback health monitoring diagnostic test, as evidenced by specific syslog messages, culminating in a device reboot with a reason code of Kernel Panic.
APT Groups using this vulnerability
While there are no identified Advanced Persistent Threat (APT) groups exploiting this vulnerability currently, it is imperative to remain vigilant. Historically, APT groups have targeted similar vulnerabilities to disrupt services and gather intelligence.
Affected Product Versions
The affected product versions encompass the following Cisco switches: Nexus 3100 Series, Nexus 3200 Series, Nexus 3400 Series, Nexus 3600 Series, Nexus 9200 Series in standalone NX-OS mode, Nexus 9300 Series in standalone NX-OS mode, and Nexus 9400 Series in standalone NX-OS mode.
Workaround and Mitigation
Cisco has issued advisories and updates to address this vulnerability. It is crucial for organizations to promptly apply the patches provided by Cisco. Additionally, network administrators should vigilantly monitor for unusual traffic patterns that may suggest exploitation attempts. Implementing network segmentation can further minimize exposure by restricting vulnerable devices from potential attackers.
References
For more detailed information, please refer to the official Cisco Security Advisory found here: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-n3kn9k-healthdos-eOqSWK4g and the National Vulnerability Database entry for CVE-2025-20111 at https://nvd.nist.gov/vuln/detail/CVE-2025-20111.
Rescana is here for you
At Rescana, we are committed to helping our clients navigate the complexities of cybersecurity. Our Third Party Risk Management (TPRM) platform offers comprehensive solutions to manage and mitigate risks posed by vulnerabilities like CVE-2025-20111. Should you have any questions or require further assistance regarding this report or other cybersecurity concerns, please reach out to us at ops@rescana.com. We are here to support your cybersecurity needs and ensure your network's integrity.