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Home - Vulnerability NotesPrint
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CERT-In Vulnerability Note CIVN-2026-0134
Denial of Service Vulnerability in CISCO

Original Issue Date:March 12, 2026

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

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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