Overview
This report discusses CVE-2025-20241, a critical vulnerability discovered in the Intermediate System-to-Intermediate System (IS-IS) feature of Cisco NX-OS Software. This vulnerability, affecting Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode, could potentially lead to system compromise or data leakage. Its severity and wide-ranging impact make this vulnerability a significant concern for all organizations using affected Cisco products.
Vulnerability Summary
CVE ID: CVE-2025-20241
Severity: Critical (CVSS 7.4)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Successful exploitation could cause an unexpected restart of the IS-IS process, resulting in a device reload and a potential Denial of Service (DoS) condition.
Affected Products
Product | Affected Versions
Cisco NX-OS Software for Cisco Nexus 3000 Series Switches | All affected versions
Cisco NX-OS Software for Cisco Nexus 9000 Series Switches in standalone NX-OS mode | All affected versions
How the Exploit Works
The vulnerability is a result of inadequate input validation when parsing an incoming IS-IS packet. An attacker could exploit this vulnerability by sending a specially crafted IS-IS packet to an affected device. Successful exploitation of this vulnerability would cause the IS-IS process to unexpectedly restart, leading to a device reload and potentially causing a Denial of Service (DoS) condition.
Conceptual Example Code
While the following is not an actual exploit code, it illustrates the general concept of how an attacker might exploit this vulnerability:
# Attacker sends a crafted IS-IS packet to the vulnerable device
send_packet --dest_ip --protocol IS-IS --payload Please note that this is a simplified conceptual example, and actual exploitation would require in-depth knowledge of the IS-IS protocol and crafting malicious payloads.
