Is CVE-2021-34767 in the CISA KEV catalog?

No. CVE-2021-34767 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-34767?

CVE-2021-34767 has a CVSS v3 base score of 7.4 (HIGH).

What is the EPSS score for CVE-2021-34767?

CVE-2021-34767 has an EPSS score of 0.78% (52th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix or mitigate CVE-2021-34767?

No published fix for CVE-2021-34767 has been found yet. Check the linked vendor advisories for guidance as it becomes available.

CVE & CISA-KEV Catalog

CVE-2021-34767

HIGH

7.4

CVSS v3

NVD

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.

CWE-670

How to fix

No published remediation has been found for this vulnerability's affected products yet.

Mitigation guidance may be in the linked vendor advisories in the References section below.

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CVSS v3 Vector

Exploitability

Attack VectorAdjacent

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeChanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

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

Exploit Intelligence

0.78%probability of exploitation in 30 days

52ndpercentile

Moderate risk: more likely to be exploited than 52% of all known CVEs.

References

Vendor Advisory1

tools.cisco.com

Related Vulnerabilities

Other CWE-670 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2020-9425	High	7.5	17%	-	Fix
CVE-2019-9946	High	7.5	3.1%	-	Fix
CVE-2024-32896	High	7.8	3.0%	KEV	-
CVE-2019-17192	Critical	9.8	2.7%	-	-
CVE-2026-38361	High	7.5	2.6%	-	-
CVE-2020-1914	Critical	9.8	2.5%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-10-30.