CVE-2022-27516: 
NixOS vulnerability analysis and mitigation

CVE-2022-27516 is a user login brute force protection functionality bypass vulnerability affecting Citrix ADC and Citrix Gateway products. The vulnerability was disclosed on November 8th, 2022, and affects multiple versions of these products including versions 13.1 before 13.1-33.47, 13.0 before 13.0-88.12, and 12.1 before 12.1-65.21. This vulnerability can only be exploited if the appliance is configured as a VPN (Gateway) or AAA virtual server, and the user lockout functionality 'Max Login Attempts' must be configured (Arctic Wolf).

The vulnerability is classified as a Protection Mechanism Failure (CWE-693) and Improper Restriction of Excessive Authentication Attempts (CWE-307). According to the National Vulnerability Database, it received a CVSS v3.1 base score of 9.8 (CRITICAL) from NIST with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H, while Citrix Systems assessed it with a CVSS score of 5.3 (MEDIUM) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N (NVD).

The vulnerability allows attackers to bypass the user login brute force protection mechanism, potentially leading to unauthorized access to affected systems. This specifically impacts systems where the appliance is configured as a VPN (Gateway) or AAA virtual server with the user lockout functionality configured (Arctic Wolf).

Citrix has released patched versions to address this vulnerability. Organizations are recommended to upgrade to Citrix ADC and Citrix Gateway versions 13.1-33.47 and later releases, 13.0-88.12 and later releases of 13.0, or 12.1-65.21 and later releases of 12.1. For FIPS and NDcPP versions, upgrade to 12.1-55.289 or later releases. Systems running versions prior to 12.1 are End of Life (EOL) and should be upgraded to supported versions (Arctic Wolf).