CVE-2016-1409: The Neighbor Discovery (ND) protocol implementation in the IPv6 stack in Cisco IOS XE 2.1 through 3.17S, IOS XR 2.0.0…

Is it exploited?

Reported, not confirmed by CISA. VulnCheck KEV lists it as exploited in the wild. CISA has not added it to its Known Exploited Vulnerabilities catalog as of 29 Oct 2026.

VulnCheck KEV lists it since 26 May 2016. It cites 2 public reports, the first from 26 May 2016.

• sec.cloudapps.cisco.com
• cve.org

How likely is exploitation in the next 30 days?

3.9%

EPSS score, percentile 90.2 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

Not scored

The CVE record carries no CVSS score.

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (1)

Which versions are affected?

Not stated. The CVE record gives vendor and product as “n/a” and the version as “unspecified”.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; VulnCheck KEV, as of 30 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 30 Oct 2026. About the data.

Description

The Neighbor Discovery (ND) protocol implementation in the IPv6 stack in Cisco IOS XE 2.1 through 3.17S, IOS XR 2.0.0 through 5.3.2, and NX-OS allows remote attackers to cause a denial of service (packet-processing outage) via crafted ND messages, aka Bug ID CSCuz66542, as exploited in the wild in May 2016.

Source: CVE List, as of 30 Oct 2026. About the data.

What to do

Advisories and patches

• 20160525 Cisco Products IPv6 Neighbor Discovery Crafted Packet Denial of Service Vulnerability (Vendor advisory)

This summary is based on the CVE record as of 30 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

The CVE record does not name affected products or versions: vendor and product are “n/a” and the version is “unspecified”.

Source: CVE List, as of 30 Oct 2026. About the data.

Timeline

Known exploited Cisco vulnerabilities

• CVE-2026-76418: Cisco Secure Firewall ASA Software and Cisco Secure FTD Software Unchecked Return Value to NULL Pointer Dereference Vulnerability (added 29 Oct 2026)
• CVE-2026-76519: Cisco Secure Email Gateway Relative Path Traversal Vulnerability (added 14 Oct 2026)
• CVE-2026-76504: Cisco Catalyst SD-WAN Manager Hex Encoding Vulnerability (added 30 Sep 2026)
• CVE-2026-76460: Cisco Identity Services Engine Incorrect Use of Privileged APIs Vulnerability (added 16 Sep 2026)
• CVE-2026-76461: Cisco Secure Email Gateway SQL Injection Vulnerability (added 14 Sep 2026)