Citrix have released a critical security update for vulnerabilities found Citrix Application Delivery Controller, Citrix Gateway, and Citrix SD-WAN WANOP appliances. The severity is critical, as a result we strongly recommend our customers to apply the updates immediately to ensure your systems are protected.
Description of Problem
Vulnerabilities have been discovered in Citrix ADC (formerly known as NetScaler ADC), Citrix Gateway (formerly known as NetScaler Gateway), and Citrix SD-WAN WANOP Edition models 4000-WO, 4100-WO, 5000-WO, and 5100-WO. These vulnerabilities, if exploited, could result in the following security issues:
| CVE-ID | Description | CWE | Affected Products | Pre-conditions | Criticality |
| CVE-2021-22955 | Unauthenticated denial of service | CWE-400: Uncontrolled Resource Consumption | Citrix ADC, Citrix Gateway | Appliance must be configured as a VPN (Gateway) or AAA virtual server | Critical |
| CVE-2021-22956 | Temporary disruption of the Management GUI, Nitro API and RPC communication | CWE-400: Uncontrolled Resource Consumption | Citrix ADC, Citrix Gateway, Citrix SD-WAN WANOP Edition | Access to NSIP or SNIP with management interface access | Low |
CVE-2021-22955: The following supported versions of Citrix ADC and Citrix Gateway are affected by this vulnerability:
- Citrix ADC and Citrix Gateway 13.0 before 13.0-83.27
- Citrix ADC and Citrix Gateway 12.1 before 12.1-63.22
- Citrix ADC and NetScaler Gateway 11.1 before 11.1-65.23
- Citrix ADC 12.1-FIPS before 12.1-55.257
CVE-2021-22956: All supported versions of Citrix ADC, Citrix Gateway, and Citrix SD-WAN WANOP Edition are affected by this vulnerability until the appliance has been configured according to the Citrix Application Delivery Controller, Citrix Gateway, and Citrix SD-WAN WANOP Edition – Management Module Configuration Reference Guide.
The following supported versions of Citrix ADC, Citrix Gateway, and Citrix SD-WAN WANOP Edition support this configuration change:
- Citrix ADC and Citrix Gateway 13.1-4.43 and later releases
- Citrix ADC and Citrix Gateway 13.0-83.27 and later releases of 13.0
- Citrix ADC and Citrix Gateway 12.1-63.22 and later releases of 12.1
- Citrix ADC and NetScaler Gateway 11.1-65.23 and later releases of 11.1
- Citrix ADC 12.1-FIPS 12.1-55.257 and later releases of 12.1-FIPS
Citrix recommends that affected customers install the relevant update as soon as possible.
CVE-2021-22956: Customers must configure their appliance according to the Citrix Application Delivery Controller, Citrix Gateway, and Citrix SD-WAN WANOP Edition – Management Module Configuration Reference Guide to address the vulnerability. This configuration change is only available in the following versions:
- Citrix ADC and Citrix Gateway 13.1-4.43 and later releases
- Citrix ADC and Citrix Gateway 13.0-83.27 and later releases of 13.0
- Citrix ADC and Citrix Gateway 12.1-63.22 and later releases of 12.1
- Citrix ADC and NetScaler Gateway 11.1-65.23 and later releases of 11.1
- Citrix ADC 12.1-FIPS 12.1-55.257 and later releases of 12.1-FIPS
- Citrix SD-WAN WANOP Edition 11.4.2 and later releases of 11.4
- Citrix SD-WAN WANOP Edition 10.2.9c and later releases of 10.2
Citrix recommends that affected customers ensure they are running a relevant version and then modify the configuration as soon as their patching schedule allows.
Changelog
| Date | Change |
| 2021-11-09 | Initial Publication |
| 2021-11-09 | Minor formatting changes |
| 2021-11-10 | Clarification regarding remediation steps for CVE-22956 |
