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Vulnerability record · CVE-2021-22955 · published 7 December 2021

CVE-2021-22955: Citrix application delivery controller firmware uncontrolled resource consumption vulnerability

Citrix · Application Delivery Controller Firmware

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.

7.5 CVSS 3.1 High EPSS 0.89% · top 42.2% CWE-400 · Uncontrolled resource consumption
7.5CVSS 3.1 base score, v2 4.3
0.89%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

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.

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

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://support.citrix.com/article/CTX330728 Vendor Advisory
https://support.citrix.com/article/CTX330728 Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2022-27518Citrix ADC and Gateway unauthenticated remote code executionCVE-2022-27518 is an unauthenticated remote arbitrary code execution flaw in Citrix Application Delivery Controller (ADC) and Gateway firmware. The C…KEVEPSS 6.7%analysed9.8CVE-2019-19781Citrix ADC and Gateway directory traversal enabling code executionCitrix Application Delivery Controller (ADC) and Gateway versions 10.5, 11.1, 12.0, 12.1, and 13.0 contain a directory traversal flaw (CWE-22). The t…KEVEPSS 100%analysed6.5CVE-2020-8193Citrix ADC and Gateway improper access control allows unauthenticated endpoint accessCitrix ADC, Citrix Gateway, and Citrix SD-WAN WAN-OP contain an improper access control flaw (CWE-284/CWE-287) that lets unauthenticated users reach …KEVEPSS 88%analysed6.5CVE-2020-8195Citrix ADC and Gateway improper input validation information disclosureCitrix ADC, Citrix Gateway, and Citrix SD-WAN WAN-OP contain improper input validation that can result in limited information disclosure to low privi…KEVEPSS 33%analysed4.3CVE-2020-8196Citrix ADC and Gateway improper access control information disclosureCitrix ADC, Citrix Gateway and Citrix SD-WAN WAN-OP appliances contain an improper access control flaw (CWE-284/CWE-287) that allows limited informat…KEVEPSS 26%analysed9.8CVE-2022-27510Citrix gateway authentication bypass via alternate path vulnerabilityUnauthorized access to Gateway user capabilitiesEPSS 1.1%9.8CVE-2022-27516Citrix gateway improper restriction of authentication attempts vulnerabilityUser login brute force protection functionality bypassEPSS 0.64%9.8CVE-2019-18225Citrix application delivery controller firmware vulnerabilityAn issue was discovered in Citrix Application Delivery Controller (ADC) and Gateway before 10.5 build 70.8, 11.x before 11.1 build 63.9, 12.0 before …EPSS 1.5%

Source: NIST National Vulnerability Database (record CVE-2021-22955), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.