CVE-2024-5492: Netscaler ADC Open Redirect Vulnerability

CVE-2024-5492 Overview

CVE-2024-5492 is an open redirect vulnerability affecting Citrix NetScaler ADC and NetScaler Gateway. This vulnerability allows a remote unauthenticated attacker to redirect users to arbitrary websites, potentially facilitating phishing attacks, credential theft, or the distribution of malware. Open redirect flaws are commonly exploited in social engineering campaigns, as attackers can craft malicious URLs that appear to originate from trusted domains.

Critical Impact

Remote unauthenticated attackers can exploit this vulnerability to redirect legitimate users to malicious websites, enabling phishing campaigns and credential harvesting attacks that abuse the trust users place in NetScaler domains.

Affected Products

• Citrix NetScaler Application Delivery Controller (all editions including FIPS and NDCPP)
• Citrix NetScaler Gateway
• Multiple versions across standard, FIPS, and NDCPP configurations

Discovery Timeline

• July 10, 2024 - CVE-2024-5492 published to NVD
• July 25, 2025 - Last updated in NVD database

Technical Details for CVE-2024-5492

Vulnerability Analysis

This vulnerability is classified as CWE-601 (URL Redirection to Untrusted Site, also known as Open Redirect). The flaw exists within the URL handling mechanisms of NetScaler ADC and NetScaler Gateway, which fails to properly validate user-supplied redirect URLs before processing redirection requests.

When a user interacts with a crafted URL pointing to the vulnerable NetScaler instance, the application redirects the user to an attacker-controlled destination without adequate verification. This occurs because the application does not enforce a whitelist of trusted redirect destinations or properly sanitize the redirect parameter.

The network-based attack vector requires user interaction, as victims must click on a malicious link to trigger the redirect. However, no authentication or special privileges are required to exploit this vulnerability, making it accessible to any remote attacker who can craft and distribute malicious URLs.

Root Cause

The root cause of CVE-2024-5492 lies in insufficient input validation of redirect URL parameters within the NetScaler web interface. The application accepts user-supplied URLs in redirect parameters without properly validating that the destination belongs to a trusted domain or follows expected patterns. This allows attackers to inject arbitrary external URLs that the application will blindly redirect users to.

Attack Vector

The attack leverages the network-accessible nature of NetScaler ADC and Gateway interfaces. An attacker crafts a malicious URL that includes a redirect parameter pointing to an attacker-controlled domain. When distributed through phishing emails, social media, or other channels, victims who click the link are initially directed to the legitimate NetScaler instance, which then automatically redirects them to the malicious destination.

The attack flow typically involves:

1. Attacker identifies a vulnerable NetScaler ADC or Gateway instance
2. Attacker constructs a URL with a malicious redirect parameter pointing to a phishing site
3. The crafted URL maintains the legitimate NetScaler domain, appearing trustworthy to users
4. When clicked, the victim is seamlessly redirected to the attacker's site
5. The attacker's site may mimic a login page to harvest credentials or deliver malware

Detection Methods for CVE-2024-5492

Indicators of Compromise

• Unusual outbound redirect patterns from NetScaler instances to external domains
• HTTP requests containing suspicious redirect parameters with external URLs
• Log entries showing redirects to domains not associated with legitimate business operations
• User reports of unexpected redirects after clicking links to NetScaler resources

Detection Strategies

• Monitor NetScaler access logs for redirect parameters containing external or unusual domains
• Implement URL filtering and reputation-based detection at the network perimeter
• Deploy web application firewalls (WAF) with rules to detect open redirect patterns
• Analyze HTTP referrer headers for suspicious redirect chains originating from NetScaler systems

Monitoring Recommendations

• Enable verbose logging on NetScaler ADC and Gateway instances to capture redirect events
• Configure SIEM correlation rules to alert on high volumes of redirects to unknown domains
• Implement user behavior analytics to identify anomalous click patterns on corporate links
• Establish baseline traffic patterns for NetScaler instances to detect deviation

How to Mitigate CVE-2024-5492

Immediate Actions Required

• Apply the latest security patches from Citrix as documented in Citrix Security Bulletin CTX677944
• Review NetScaler configurations for any custom redirect handling that may introduce additional risk
• Educate users about the risks of clicking links, even those appearing to originate from trusted domains
• Implement network-level URL filtering to block known malicious redirect destinations

Patch Information

Citrix has released security updates to address this vulnerability. Administrators should consult the Citrix Security Advisory CTX677944 for specific version information and upgrade guidance. The advisory covers both CVE-2024-5491 and CVE-2024-5492, so organizations should ensure patches address both vulnerabilities.

Workarounds

• Configure web application firewall rules to validate and restrict redirect parameters
• Implement allowlists for permitted redirect destinations at the network or application level
• Consider deploying a reverse proxy with URL inspection capabilities in front of vulnerable instances
• Block or sanitize redirect parameters at the load balancer or WAF until patches can be applied

# Example WAF rule concept for blocking suspicious redirects
# Note: Consult vendor documentation for specific implementation
# Block requests with redirect parameters pointing to external domains
# Review and customize allowed_domains based on organizational needs