CVE-2021-1268

7.4 HIGH 0.5% exploit odds Fix listed

What it is

A vulnerability in the IPv6 protocol handling of the management interfaces of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause an IPv6 flood on the management interface network of an affected device. The vulnerability exists because the software incorrectly forwards IPv6 packets that have an IPv6 node-local multicast group address destination and are received on the management interfaces. An attacker could exploit this vulnerability by connecting to the same network as the management interfaces and injecting IPv6 packets that have an IPv6 node-local multicast group address destination. A successful exploit could allow the attacker to cause an IPv6 flood on the corresponding network. Depending on the number of Cisco IOS XR Software nodes on that network segment, exploitation could cause excessive network traffic, resulting in network degradation or a denial of service (DoS) condition.

At a glance

Exploitability: Can be exploited from the same network segment without logging in. High risk of service disruption.
Exploit odds: 0.5% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2021-02-04 17:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 03:31 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.5% in the next 30 days (EPSS).
Severity: 7.4 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2021-02-04 17:15 UTC
Last modified: 2026-06-17 03:31 UTC
Exploit probability: 0.5% · EPSS, next 30 days
Weakness: CWE-1076
Record status: Modified

Affected

Cisco iOS Xr < 6.7.3
Cisco iOS Xr < 7.1.3
Cisco iOS Xr < 7.2.2
Cisco iOS Xr 7.3.0

Attack profile CVSS 3.1 · 7.4

Attack vector: Adjacent network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Changed
Confidentiality: None
Integrity: None
Availability: High

Raw vector

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

Is it in your code?

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Read https://cve-list.com/agent/cve/CVE-2021-1268.md and follow it. Check whether this project is affected by CVE-2021-1268. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record