CVE-2021-34767: Cisco IOS XE Software for Catalyst 9800 Series Wireless Controllers IPv6 Denial of Service Vulnerability

Severity: high (CVSS 7.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-09-23 · updated 2026-06-17
Weakness: CWE-670

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 products

Cisco IOS XE: 3.15.1xbs, 3.15.2xbs, 16.7.1, 16.7.1a, 16.7.1b, 16.7.2 (+86)

References

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