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Denial of Service Vulnerability in CISCO

Indian – Computer Emergency Response Team (https://www.cert-in.org.in)

Severity Rating: HIGH

Systems Affected

Cisco IOS XR Software

NCS 5700 Series line cards with the following products IDs (PIDs):

NC57-18DD-S

NC57-24DD

NC57-36H-SE

NC57-36H6D-S

NC57-MOD-S

NCS 5700 Series Fixed Chassis with the following PIDs:

NCS-57B1-5D24H-SE

NCS-57B1-5DSE-SYS

NCS-57B1-6D24-SYS

NCS-57B1-6D24H-S

Overview

A vulnerability has been reported in handling of an Egress Packet Network Interface (EPNI) Aligner interrupt in Cisco IOS XR Software for Cisco Network Convergence System (NCS) 5500 Series with NC57 line cards and Cisco NCS 5700 Routers and Cisco IOS XR Software for Third Party Software could allow an unauthenticated, remote attacker to cause the network processing unit (NPU) and ASIC to stop processing, preventing traffic from traversing the interface.

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 corruption of packets in specific cases when an EPNI Aligner interrupt is triggered while an affected device is experiencing heavy transit traffic. An attacker could exploit this vulnerability by sending a continuous flow of crafted packets to an interface of the affected device.

Successful exploitation of this vulnerability could allow the attacker to cause persistent, heavy packet loss, resulting in 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-xrncs-epni-int-dos-TWMffUsN

Vendor Information

CISCO

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-xrncs-epni-int-dos-TWMffUsN

References

CISCO

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-xrncs-epni-int-dos-TWMffUsN

CVE Name

CVE-2026-20118

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Thanks and Regards,

CERT-In

Incident Response Help Desk

e-mail: incident@cert-in.org.in

Phone: +91-11-22902657

Toll Free Number: 1800-11-4949

Toll Free Fax : 1800-11-6969

Web: http://www.cert-in.org.in

PGP Fingerprint: A768 083E 4475 5725 B81A A379 2156 C0C0 B620 D0B4

PGP Key information:

https://www.cert-in.org.in/s2cMainServlet?pageid=CONTACTUS

Postal address:

Indian Computer Emergency Response Team (CERT-In)

Ministry of Electronics and Information Technology

Government of India

Electronics Niketan

6, C.G.O. Complex

New Delhi-110 003

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