CVE-2021-22955

Name: CVE-2021-22955
Creator: NVD / NIST
Published: 2021-12-07T14:15:08.89+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 0.89%

Last modified Jun 17, 2026

CVE-2021-22955 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. A unauthenticated denial of service vulnerability exists in Citrix ADC <13.0-83.27, <12.1-63.22 and 11.1-65.23 when configured as a VPN (Gateway) or AAA virtual server could allow an attacker to cause a temporary disruption of the Management GUI, Nitro API, and RPC communication.. EPSS estimates a 0.89% chance of exploitation in the next 30 days.

Description

A unauthenticated denial of service vulnerability exists in Citrix ADC <13.0-83.27, <12.1-63.22 and 11.1-65.23 when configured as a VPN (Gateway) or AAA virtual server could allow an attacker to cause a temporary disruption of the Management GUI, Nitro API, and RPC communication.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

0.89%

54.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Citrix	Application Delivery Controller Firmware	<= 11.1-65.23
Citrix	Application Delivery Controller Firmware	>= 12.1, < 12.1-63.22
Citrix	Application Delivery Controller Firmware	>= 13.0, < 13.0-83.27
Citrix	Gateway	< 11.1-65.23
Citrix	Gateway	>= 12.1, < 12.1-63.22
Citrix	Gateway	>= 13.0, < 13.0-83.27

References

https://support.citrix.com/article/CTX330728Vendor Advisory
https://support.citrix.com/article/CTX330728Vendor Advisory

Timeline

Published: Dec 7, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-22955?

How severe is CVE-2021-22955?

CVE-2021-22955 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.89% probability of exploitation in the next 30 days.

How do I fix CVE-2021-22955?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-22955?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST