CVE-2023-6548: Citrix NetScaler ADC RCE Vulnerability

CVE-2023-6548 Overview

CVE-2023-6548 is a code injection vulnerability affecting Citrix NetScaler ADC and NetScaler Gateway appliances. The vulnerability allows an authenticated attacker with low privileges and access to the management interface (NSIP, CLIP, or SNIP) to perform remote code execution. This flaw stems from improper control of code generation (CWE-94), enabling attackers to inject and execute arbitrary code on the management interface of affected devices.

Critical Impact

This vulnerability is actively exploited in the wild and has been added to CISA's Known Exploited Vulnerabilities (KEV) catalog. Authenticated attackers can achieve remote code execution on the management interface, potentially compromising the entire network infrastructure protected by these appliances.

Affected Products

• Citrix NetScaler Application Delivery Controller (ADC) - Standard, FIPS, and NDcPP editions
• Citrix NetScaler Gateway
• Multiple versions across different deployment configurations

Discovery Timeline

• 2024-01-17 - CVE-2023-6548 published to NVD
• 2025-10-24 - Last updated in NVD database

Technical Details for CVE-2023-6548

Vulnerability Analysis

This code injection vulnerability exists within the management interface of NetScaler ADC and NetScaler Gateway appliances. The flaw allows an authenticated user with low-level privileges to inject malicious code that gets executed by the system. The attack requires network access and authentication credentials, but only low-level privileges are needed to exploit the vulnerability.

The vulnerability is particularly dangerous because NetScaler devices are typically positioned at critical network boundaries, serving as application delivery controllers and VPN gateways. Successful exploitation grants attackers the ability to execute arbitrary commands on the management interface, which could lead to complete device compromise, lateral movement within the network, or data exfiltration.

Root Cause

The root cause of CVE-2023-6548 is improper control of code generation (CWE-94) within the management interface handling code. The application fails to properly sanitize or validate user-controlled input before using it in code generation contexts, allowing attackers to inject arbitrary code that the system subsequently executes. This class of vulnerability typically occurs when dynamic code execution mechanisms do not adequately distinguish between trusted code and untrusted user input.

Attack Vector

The attack vector for this vulnerability requires:

1. Network Access: The attacker must have network connectivity to the management interface (NSIP - NetScaler IP, CLIP - Cluster IP, or SNIP - Subnet IP with management access enabled)
2. Authentication: Valid credentials with at least low-privileged access to the management interface
3. No User Interaction: Once authenticated, the attacker can exploit the vulnerability without requiring any additional user interaction

Upon successful exploitation, the attacker can execute arbitrary code on the management interface with the privileges of the NetScaler service. This could enable persistence mechanisms, credential harvesting, configuration manipulation, or pivoting to other network resources. The management interface typically has elevated access to system functions, making this a high-impact compromise scenario.

Detection Methods for CVE-2023-6548

Indicators of Compromise

• Unusual process execution or command-line activity on NetScaler management interface
• Unexpected network connections originating from NetScaler management IPs to external or internal hosts
• Anomalous authentication patterns or login attempts to management interfaces
• Suspicious modifications to NetScaler configuration files or scripts

Detection Strategies

• Monitor authentication logs for the NetScaler management interface for unusual access patterns or failed login attempts followed by successful logins
• Implement network traffic analysis to detect anomalous traffic from management interface IPs (NSIP, CLIP, SNIP)
• Deploy endpoint detection on NetScaler appliances where supported to identify code injection attempts
• Review and alert on any unexpected process creation or script execution on the management plane

Monitoring Recommendations

• Enable comprehensive logging on NetScaler ADC and Gateway management interfaces
• Configure SIEM rules to alert on management interface access from unexpected source IPs
• Monitor for indicators listed in CISA's KEV catalog and threat intelligence feeds
• Implement network segmentation monitoring to detect lateral movement attempts from compromised appliances

How to Mitigate CVE-2023-6548

Immediate Actions Required

• Apply the security patches provided by Citrix immediately as this vulnerability is actively exploited
• Restrict management interface access to trusted networks and IP addresses only
• Audit all accounts with management interface access and enforce least-privilege principles
• Monitor for indicators of compromise on all NetScaler ADC and Gateway appliances

Patch Information

Citrix has released security updates to address this vulnerability. Organizations should consult the Citrix Security Bulletin CTX584986 for detailed patch information and affected version numbers. Due to active exploitation, CISA has added this vulnerability to the Known Exploited Vulnerabilities Catalog, mandating federal agencies to apply remediations.

Workarounds

• Restrict access to the management interface by implementing strict network ACLs limiting access to trusted administrator workstations only
• Disable management access on SNIP interfaces unless absolutely required for operations
• Implement multi-factor authentication for all management interface access
• Consider temporarily disabling management interface network access if patching cannot be performed immediately

# Example: Restrict management interface access via ACL
# Note: Consult Citrix documentation for your specific deployment
# Add ACL to restrict NSIP management access
add ns acl restrict_mgmt_access ALLOW -srcIP 10.0.0.0-10.0.0.255 -destPort 80,443 -protocol TCP
apply ns acls

# Disable management access on SNIP if not required
set ns ip <SNIP_ADDRESS> -mgmtAccess DISABLED