CVE-2021-34767

Cisco IOS XE Software for Catalyst 9800 Series Wireless Controllers IPv6 Denial of Service Vulnerability

HIGH

7.4

CVSS Score

Published: September 23, 2021 at 02:26 AM UTC

Updated: June 17, 2026 at 03:56 AM UTC

9 products affected across 1 vendorIOS XeCatalyst 9800-LCatalyst 9800-80

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Severity

HIGH7.4

Exploit prediction

EPSS 0.8%

SSVC

No known exploit

Description

A vulnerability in IPv6 traffic processing of Cisco IOS XE Wireless Controller Software for Cisco Catalyst 9000 Family Wireless Controllers could allow an unauthenticated, adjacent attacker to cause a Layer 2 (L2) loop in a configured VLAN, resulting in a denial of service (DoS) condition for that VLAN. The vulnerability is due to a logic error when processing specific link-local IPv6 traffic. An attacker could exploit this vulnerability by sending a crafted IPv6 packet that would flow inbound through the wired interface of an affected device. A successful exploit could allow the attacker to cause traffic drops in the affected VLAN, thus triggering the DoS condition.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

IOS Xe · Cisco

95%

cisco-catalyst-9800 (environment) · cisco-catalyst-9800-40 (environment) · cisco-catalyst-9800-80 (environment) · cisco-catalyst-9800-cl (environment) · cisco-catalyst-9800-embedded-wireless-controller (environment) · cisco-catalyst-9800-l (environment) · cisco-catalyst-9800-l-c (environment) · cisco-catalyst-9800-l-f (environment)

Catalyst 9800 · Ciscodevice

80%

All versions

Catalyst 9800-40 · Ciscodevice

80%

All versions

Catalyst 9800-80 · Ciscodevice

80%

All versions

Catalyst 9800-Cl · Ciscodevice

80%

All versions