What is CVE-2021-1611?

CVE-2021-1611 is a high-severity vulnerability in Cisco Catalyst 9800, classified under CWE-399. CVSS score: 8.6/10. Published 2021-09-23.

How severe is CVE-2021-1611?

High severity. CVSS v3 base score is 8.6 out of 10.

Vulnerability in Cisco Catalyst 9800

CVE-2021-1611

A vulnerability in Ethernet over GRE (EoGRE) packet processing of Cisco IOS XE Wireless Controller Software for the Cisco Catalyst 9800 Family Wireless Controller, Embedded Wireless Controller, and Embedded Wireless on Catalyst 9000 Series Switches could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper processing of malformed EoGRE packets. An attacker could exploit this vulnerability by sending malicious packets to the affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

Published 2021-09-23 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.013 (71.0th percentile), scored 2026-11-02.

Low probability of exploitation in the next 30 days, but still tracked. 71st percentile — 71.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.013 · newest: 0.013 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-399

References

tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ewlc-gre… (vendor-advisory, Patch, Vendor Advisory)

Frequently asked questions

What is CVE-2021-1611?: CVE-2021-1611 is a high-severity vulnerability in Cisco Catalyst 9800, classified under CWE-399. CVSS score: 8.6/10. Published 2021-09-23.
How severe is CVE-2021-1611?: High severity. CVSS v3 base score is 8.6 out of 10.