Detections
Analytics

Cisco Nexus 3000 9000 Series Switches Intermediate System-to-Intermediate System DoS (cisco-sa-n39k-isis-dos-JhJA8Rfx)

high Nessus Plugin ID 303931

Synopsis

The remote device is missing a vendor-supplied security patch

Description

According to its self-reported version, Cisco NX-OS Software is affected by a vulnerability.

 - 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. (CVE-2025-20241)

Please see the included Cisco BIDs and Cisco Security Advisory for more information.

Solution

Upgrade to the relevant fixed version referenced in Cisco bug ID CSCwn49153

See Also

http://www.nessus.org/u?1e98404c

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwn49153

Plugin Details

Severity: High

ID: 303931

File Name: cisco-sa-n39k-isis-dos-JhJA8Rfx.nasl

Version: 1.1

Type: combined

Family: CISCO

Published: 3/27/2026

Updated: 3/27/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v2

Risk Factor: Medium

Base Score: 6.1

Temporal Score: 4.5

Vector: CVSS2#AV:A/AC:L/Au:N/C:N/I:N/A:C

CVSS Score Source: CVE-2025-20241

CVSS v3

Risk Factor: High

Base Score: 7.4

Temporal Score: 6.4

Vector: CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:cisco:nx-os

Required KB Items: Host/Cisco/NX-OS/Version, Host/Cisco/NX-OS/Model, Host/Cisco/NX-OS/Device

Exploit Ease: No known exploits are available

Patch Publication Date: 8/27/2025

Vulnerability Publication Date: 8/27/2025

Reference Information

CVE: CVE-2025-20241

CWE: 733

CISCO-SA: cisco-sa-n39k-isis-dos-JhJA8Rfx

IAVA: 2025-A-0635

CISCO-BUG-ID: CSCwn49153