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Home - Vulnerability NotesPrint
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CERT-In Vulnerability Note CIVN-2026-0133
Denial of Service Vulnerability in CISCO

Original Issue Date:March 12, 2026

Severity Rating: HIGH

Systems Affected

  • Cisco IOS XR Software

Overview

A vulnerability has been reported in the Intermediate System-to-Intermediate System (IS-IS) multi-instance routing feature of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause the IS-IS process to restart unexpectedly.

Target Audience: 
All IT administrators and individuals responsible for maintaining and updating in Software.

Risk Assessment:
High risk of data manipulation and service disruption.

Impact Assessment:
Potential impact on confidentiality, integrity, and availability of the system.

Description

This vulnerability exists due to insufficient input validation of ingress IS-IS packets. An attacker could exploit this vulnerability by sending crafted IS-IS packets to an affected device after forming an adjacency.

Successful exploitation of this vulnerability could allow the attacker to cause the IS-IS process to restart unexpectedly, resulting in a temporary loss of connectivity to advertised networks and a denial of service (DoS) condition.

Solution

Apply appropriate updates as mentioned in Cisco Advisory
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK

Vendor Information

CISCO
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK

References

CISCO
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-isis-dos-kDMxpSzK

CVE Name
CVE-2026-20074

Disclaimer

The information provided herein is on "as is" basis, without warranty of any kind.

Contact Information

Email: info@cert-in.org.in
Phone: +91-11-22902657

Postal address

Indian Computer Emergency Response Team (CERT-In)
Ministry of Electronics and Information Technology
Government of India
Electronics Niketan
6, CGO Complex, Lodhi Road,
New Delhi - 110 003
India

 
Indian Computer Emergency Response Team - CERT-In, Ministry of Electronics and Information Technology, Government of India.
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