CVE-2025-20241
Cisco Nexus 3000 and 9000 Series Switches IS-IS Protocol <TBD> Denial of Service Vulnerability
Description
A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) feature of Cisco NX-OS Software for Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, adjacent attacker to cause the IS-IS process to unexpectedly restart, which could cause an affected device to reload. This vulnerability is due to insufficient input validation when parsing an ingress IS-IS packet. An attacker could exploit this vulnerability by sending a crafted IS-IS packet to an affected device. A successful exploit could allow the attacker to cause the unexpected restart of the IS-IS process, which could cause the affected device to reload, resulting in a denial of service (DoS) condition. Note: The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device.
INFO
Published Date :
Aug. 27, 2025, 5:15 p.m.
Last Modified :
Aug. 29, 2025, 4:24 p.m.
Remotely Exploit :
No
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Apply vendor patches to Cisco Nexus devices.
- Update NX-OS to a fixed version.
- Restrict network access to IS-IS process.
- Monitor IS-IS traffic for malicious packets.
Public PoC/Exploit Available at Github
CVE-2025-20241 has a 1 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-20241.
| URL | Resource |
|---|---|
| https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-n39k-isis-dos-JhJA8Rfx |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-20241 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-20241
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
A collection of things I learned today. 今日学んだことの記録。
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2025-20241 vulnerability anywhere in the article.
-
The Hacker News
⚡ Weekly Recap: WhatsApp 0-Day, Docker Bug, Salesforce Breach, Fake CAPTCHAs, Spyware App & More
Cybersecurity today is less about single attacks and more about chains of small weaknesses that connect into big risks. One overlooked update, one misused account, or one hidden tool in the wrong hand ... Read more
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CybersecurityNews
Cisco Nexus 3000 and 9000 Series Vulnerability Let Attackers Trigger DoS Attack
Cisco has issued a High-severity security advisory alerting customers to a critical vulnerability in the Intermediate System-to-Intermediate System (IS-IS) feature of NX-OS Software for Cisco Nexus 30 ... Read more
-
Daily CyberSecurity
Cisco Warns of High-Severity DoS Flaw (CVE-2025-20241) in Nexus Switches
Cisco Systems has published a security advisory detailing a high-severity denial-of-service (DoS) vulnerability affecting Cisco Nexus 3000 and 9000 Series Switches running NX-OS software. The flaw, tr ... Read more
-
Daily CyberSecurity
An Espionage System: NSA, CISA, & Partners Expose Chinese APT Groups
In a multinational alert, the U.S. National Security Agency (NSA), CISA, FBI, and partners from more than a dozen allied nations have released a Joint Cybersecurity Advisory (CSA) exposing how Chinese ... Read more
-
Daily CyberSecurity
A Single Packet Can Crash a DHCP Server: High-Severity Flaw CVE-2025-40779 Found in Kea
The Internet Systems Consortium (ISC) has released a security advisory addressing a high-severity vulnerability in its widely used Kea DHCP server. The flaw, tracked as CVE-2025-40779 with a CVSS scor ... Read more
The following table lists the changes that have been made to the
CVE-2025-20241 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Aug. 27, 2025
Action Type Old Value New Value Added Description A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) feature of Cisco NX-OS Software for Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, adjacent attacker to cause the IS-IS process to unexpectedly restart, which could cause an affected device to reload. This vulnerability is due to insufficient input validation when parsing an ingress IS-IS packet. An attacker could exploit this vulnerability by sending a crafted IS-IS packet to an affected device. A successful exploit could allow the attacker to cause the unexpected restart of the IS-IS process, which could cause the affected device to reload, resulting in a denial of service (DoS) condition. Note: The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device. Added CVSS V3.1 AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H Added CWE CWE-733 Added Reference https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-n39k-isis-dos-JhJA8Rfx