CVE-2022-27510: Citrix Gateway Auth Bypass Vulnerability

CVE-2022-27510 Overview

CVE-2022-27510 is an authentication bypass vulnerability affecting Citrix Gateway and Citrix Application Delivery Controller (ADC). The flaw allows a remote, unauthenticated attacker to gain access to user capabilities normally restricted to authenticated Gateway users. The vulnerability is exploitable over the network without user interaction, and Citrix published a security bulletin addressing it alongside CVE-2022-27513 and CVE-2022-27516. The issue is tracked under [CWE-288] (Authentication Bypass Using an Alternate Path or Channel) and [CWE-287] (Improper Authentication).

Critical Impact
Remote, unauthenticated attackers can bypass authentication controls and access Gateway user functionality on internet-facing Citrix appliances.

Affected Products

Citrix Gateway
Citrix Application Delivery Controller (ADC)
Citrix Application Delivery Controller Firmware (including FIPS and NDcPP editions)

Discovery Timeline

2022-11-08 - CVE-2022-27510 published to NVD
2022-11-08 - Citrix releases security bulletin CTX463706 with patched firmware
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-27510

Vulnerability Analysis

The vulnerability exists in the authentication logic that gates access to Gateway user functionality on Citrix ADC and Citrix Gateway appliances. An attacker can reach this functionality through an alternate path that does not enforce authentication checks, resulting in unauthorized access to capabilities reserved for legitimate Gateway users. Exploitation requires only network access to the appliance and no prior credentials, which makes internet-exposed Gateway deployments the primary risk surface. Successful exploitation impacts confidentiality, integrity, and availability of resources protected by the Gateway. Citrix advisory CTX463706 confirms the issue applies only to appliances configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or as an AAA virtual server.

Root Cause

The root cause is improper authentication enforcement on a code path that exposes Gateway user functions. The affected logic does not adequately validate session state or credentials before granting access, mapping to [CWE-288] and [CWE-287]. The flaw is a design-level authentication bypass rather than a memory corruption or injection issue.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker sends crafted requests directly to the Gateway or AAA virtual server endpoint exposed by the appliance. Because Citrix Gateway is typically deployed at the network perimeter for remote access, the attack surface is reachable from the public internet in most production deployments. See the Citrix Security Bulletin CTX463706 for the full list of affected builds and remediation guidance.

No public proof-of-concept exploit code has been released. The vulnerability is described in prose only because no verified exploitation code is available from authoritative sources.

Detection Methods for CVE-2022-27510

Indicators of Compromise

Unexpected authentication or session events in ns.log originating from external IP addresses without preceding login activity.
New or unrecognized VPN, ICA Proxy, or AAA sessions established outside normal business hours or from atypical geolocations.
Outbound connections from the ADC management plane to unknown hosts, indicating possible post-exploitation activity.

Detection Strategies

Inventory all Citrix ADC and Gateway appliances and compare running firmware against the fixed versions listed in CTX463706.
Inspect appliance configuration to confirm whether a Gateway (VPN vserver, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server is configured, which is required for the appliance to be vulnerable.
Correlate Gateway authentication logs with corporate identity provider logs to identify sessions that lack a matching authentication event.

Monitoring Recommendations

Forward Citrix ADC syslog and AAA logs to a centralized SIEM and alert on authentication anomalies and abnormal session creation rates.
Monitor north-south traffic to Gateway virtual server IPs for spikes in unauthenticated requests against AAA or VPN endpoints.
Track administrative configuration changes on the appliance and alert on out-of-band modifications.

How to Mitigate CVE-2022-27510

Immediate Actions Required

Upgrade affected Citrix ADC and Citrix Gateway appliances to the fixed firmware builds listed in Citrix advisory CTX463706.
If patching cannot be performed immediately, restrict network reachability of the Gateway and AAA virtual servers to known IP ranges.
Review Gateway and AAA session logs for indicators of unauthorized access since the appliance was last patched.

Patch Information

Citrix released fixed firmware for Citrix ADC and Citrix Gateway in the November 8, 2022 security bulletin. Administrators should refer to the Citrix Security Bulletin CTX463706 for the complete list of fixed builds across the 12.1, 13.0, and 13.1 release trains, including FIPS and NDcPP variants. Citrix-managed Citrix Gateway service customers are not impacted.

Workarounds

Disable the Gateway and AAA virtual servers on appliances that do not require them, since the vulnerability only affects appliances configured in these roles.
Place a Web Application Firewall in front of the Gateway to filter requests targeting authentication endpoints until the firmware is upgraded.
Enforce network-layer access control lists that limit reachability of the appliance management and user planes to trusted networks.

bash

# Verify the running firmware version on a Citrix ADC/Gateway appliance
show ns version

# List configured Gateway and AAA virtual servers to determine exposure
show vpn vserver
show authentication vserver