---
title: "CVE-2026-76505: Cisco IOS XR Software - Denial of Service"
description: "Cisco IOS XR Software on Cisco ASR 9000, 9900 Series, and ASR 9902/9903 routers contains a denial of service vulnerability caused by incorrect handling of crafted IPv4 packets on line card interfaces, letting unauthenticated remote attackers cause line card resets or shutdowns, exploit requires crafted IPv4 packets targeting for-us traffic."
url: https://panop.io/threat-heartbeat/CVE-2026-76505/
---

# CVE-2026-76505 Cisco IOS XR Software - Denial of Service

Cisco IOS XR Software on Cisco ASR 9000, 9900 Series, and ASR 9902/9903 routers contains a denial of service vulnerability caused by incorrect handling of crafted IPv4 packets on line card interfaces, letting unauthenticated remote attackers cause line card resets or shutdowns, exploit requires crafted IPv4 packets targeting for-us traffic.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-76505)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Published

21 October 2026

Updated

22 October 2026

Weakness

[CWE-20](https://cwe.mitre.org/data/definitions/20.html)

## Vendor fix

Update to the latest Cisco IOS XR Software version that addresses this vulnerability.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-76505](https://nvd.nist.gov/vuln/detail/CVE-2026-76505)
- [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr9k-tUyxcyXN](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr9k-tUyxcyXN)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

Panop answers these inside your environment, for this CVE and every other finding.

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