CVE-2025-20241

Cisco Nexus 3000 and 9000 Series Switches IS-IS Protocol <TBD> Denial of Service Vulnerability

Published Aug 27, 2025 CVSS 3.1 · 7.4 High EPSS < 1% KEV · Not listed

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.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Cisco

Cisco NX-OS Software

unknown

Version	Status	Constraints
`9.2(3)`	affected	—
`7.0(3)I5(2)`	affected	—
`6.0(2)A8(7a)`	affected	—
`7.0(3)I4(5)`	affected	—
`7.0(3)I4(6)`	affected	—
`7.0(3)I4(3)`	affected	—
`9.2(2v)`	affected	—
`7.0(3)I4(7)`	affected	—
`7.0(3)I4(1)`	affected	—
`7.0(3)I4(8)`	affected	—
`7.0(3)I4(2)`	affected	—
`6.0(2)A8(11)`	affected	—
`9.2(1)`	affected	—
`9.2(2t)`	affected	—
`9.2(3y)`	affected	—
`7.0(3)I4(1t)`	affected	—
`7.0(3)I7(6z)`	affected	—
`9.3(2)`	affected	—
`7.0(3)F3(3)`	affected	—
`7.0(3)I7(3z)`	affected	—
`7.0(3)IM7(2)`	affected	—
`6.0(2)A8(11b)`	affected	—
`7.0(3)I7(5a)`	affected	—
`7.0(3)I6(1)`	affected	—
`7.0(3)I5(3b)`	affected	—
`9.2(4)`	affected	—
`6.0(2)A8(10)`	affected	—
`6.0(2)A8(2)`	affected	—
`7.0(3)IC4(4)`	affected	—
`7.0(3)F3(3c)`	affected	—
`7.0(3)F3(1)`	affected	—
`7.0(3)F3(5)`	affected	—
`7.0(3)I7(2)`	affected	—
`7.0(3)I5(3)`	affected	—
`7.0(3)I7(3)`	affected	—
`6.0(2)A8(6)`	affected	—
`7.0(3)I6(2)`	affected	—
`6.0(2)A8(5)`	affected	—
`9.3(1)`	affected	—
`6.0(2)A8(7)`	affected	—
`7.0(3)I7(6)`	affected	—
`6.0(2)A8(11a)`	affected	—
`7.0(3)I4(8z)`	affected	—
`7.0(3)I4(9)`	affected	—
`7.0(3)I7(4)`	affected	—
`7.0(3)I7(7)`	affected	—
`6.0(2)A8(9)`	affected	—
`6.0(2)A8(1)`	affected	—
`6.0(2)A8(10a)`	affected	—
`7.0(3)I5(1)`	affected	—
`9.3(1z)`	affected	—
`9.2(2)`	affected	—
`7.0(3)F3(4)`	affected	—
`7.0(3)I4(8b)`	affected	—
`6.0(2)A8(3)`	affected	—
`7.0(3)I4(6t)`	affected	—
`7.0(3)I5(3a)`	affected	—
`6.0(2)A8(8)`	affected	—
`7.0(3)I7(5)`	affected	—
`7.0(3)F3(3a)`	affected	—
`6.0(2)A8(4)`	affected	—
`7.0(3)I4(8a)`	affected	—
`7.0(3)F3(2)`	affected	—
`7.0(3)I4(4)`	affected	—
`7.0(3)I7(1)`	affected	—
`7.0(3)IA7(2)`	affected	—
`7.0(3)IA7(1)`	affected	—
`6.0(2)A8(7b)`	affected	—
`6.0(2)A8(4a)`	affected	—
`9.3(3)`	affected	—
`7.0(3)I7(8)`	affected	—
`9.3(4)`	affected	—
`9.3(5)`	affected	—
`7.0(3)I7(9)`	affected	—
`9.3(6)`	affected	—
`10.1(2)`	affected	—
`10.1(1)`	affected	—
`9.3(5w)`	affected	—
`9.3(7)`	affected	—
`9.3(7k)`	affected	—
`7.0(3)I7(9w)`	affected	—
`10.2(1)`	affected	—
`9.3(7a)`	affected	—
`9.3(8)`	affected	—
`7.0(3)I7(10)`	affected	—
`10.2(1q)`	affected	—
`10.2(2)`	affected	—
`9.3(9)`	affected	—
`10.1(2t)`	affected	—
`10.2(3)`	affected	—
`10.2(3t)`	affected	—
`9.3(10)`	affected	—
`10.2(2a)`	affected	—
`10.3(1)`	affected	—
`10.2(4)`	affected	—
`10.3(2)`	affected	—
`9.3(11)`	affected	—
`10.3(3)`	affected	—
`10.2(5)`	affected	—
`9.3(12)`	affected	—
`10.2(3v)`	affected	—
`10.4(1)`	affected	—
`10.3(99w)`	affected	—
`10.2(6)`	affected	—
`10.3(3w)`	affected	—
`10.3(99x)`	affected	—
`10.3(3o)`	affected	—
`10.3(4)`	affected	—
`10.3(3p)`	affected	—
`10.3(4a)`	affected	—
`10.4(2)`	affected	—
`10.3(3q)`	affected	—
`9.3(13)`	affected	—
`10.3(5)`	affected	—
`10.2(7)`	affected	—
`10.4(3)`	affected	—
`10.3(3x)`	affected	—
`10.3(4g)`	affected	—
`10.5(1)`	affected	—
`10.2(8)`	affected	—
`10.3(3r)`	affected	—
`10.3(6)`	affected	—
`9.3(14)`	affected	—
`10.4(4)`	affected	—
`10.3(4h)`	affected	—
`10.5(2)`	affected	—
`10.4(4g)`	affected	—

No data.

Vendor	Product	Versions
Cisco	Nexus	—
Cisco	Nexus 3000	—
Cisco	Nexus 9000	—
Cisco	Nx-os	—

Remediation

No solution or workaround provided in the CVE record

Tracking

Advisories

Source	ID	Title
EUVD	EUVD-2025-27686	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.

Metrics

No CVSS v4.0

Attack Vector Adjacent Network

Attack Complexity Low

Privileges Required None

Scope Changed

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.278% probability within 30 days)

Exploitation none

Automatable no

Technical Impact partial

References

Link	Providers
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-n39k-isis-dos-JhJA8Rfx

History

Aug 27, 2025 10:00 PM First appearance in the feed. Affected vendors updated View changes

Type	Values Removed	Values Added
First Time appeared		Cisco Cisco nexus Cisco nexus 3000 Cisco nexus 9000 Cisco nx-os
Vendors & Products		Cisco Cisco nexus Cisco nexus 3000 Cisco nexus 9000 Cisco nx-os

Aug 27, 2025 7:15 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Aug 27, 2025 4:45 PM Description updated. Title updated. Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values 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.
Title		Cisco Nexus 3000 and 9000 Series Switches IS-IS Protocol <TBD> Denial of Service Vulnerability
Weaknesses		CWE-733
References		https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-n39k-isis-dos-JhJA8Rfx
Metrics		cvssV3_1 `{'score': 7.4, 'vector': 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H'}`