CVE-2024-5491
📋 TL;DR
CVE-2024-5491 is a Denial of Service vulnerability in NetScaler ADC and NetScaler Gateway appliances. Attackers can exploit this vulnerability to crash the service, causing service disruption for legitimate users. Organizations using affected NetScaler ADC and Gateway versions are impacted.
💻 Affected Systems
- NetScaler ADC
- NetScaler Gateway
📦 What is this software?
Netscaler Application Delivery Controller by Citrix
View all CVEs affecting Netscaler Application Delivery Controller →
Netscaler Application Delivery Controller by Citrix
View all CVEs affecting Netscaler Application Delivery Controller →
Netscaler Application Delivery Controller by Citrix
View all CVEs affecting Netscaler Application Delivery Controller →
Netscaler Application Delivery Controller by Citrix
View all CVEs affecting Netscaler Application Delivery Controller →
Netscaler Application Delivery Controller by Citrix
View all CVEs affecting Netscaler Application Delivery Controller →
⚠️ Risk & Real-World Impact
Worst Case
Complete service outage of NetScaler ADC/Gateway, disrupting all application access and network traffic routing through the appliance.
Likely Case
Service disruption causing temporary unavailability of applications and services behind the NetScaler, requiring manual restart.
If Mitigated
Minimal impact with proper network segmentation and monitoring allowing quick detection and response.
🎯 Exploit Status
Denial of Service vulnerabilities typically have low exploitation complexity and may not require authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Citrix advisory CTX677944 for specific patched versions
Vendor Advisory: https://support.citrix.com/article/CTX677944/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20245491-and-cve20245492
Restart Required: Yes
Instructions:
1. Review Citrix advisory CTX677944. 2. Identify affected versions. 3. Download and apply appropriate patches from Citrix downloads. 4. Schedule maintenance window for restart. 5. Verify patch application and functionality.
🔧 Temporary Workarounds
Network Access Control
allRestrict network access to NetScaler management interfaces to trusted IPs only
Configure ACLs on upstream firewalls to limit access to NetScaler IPs
Rate Limiting
allImplement rate limiting on network traffic to NetScaler interfaces
Configure rate limiting policies on NetScaler or upstream devices
🧯 If You Can't Patch
- Implement strict network segmentation and firewall rules to limit access to NetScaler appliances
- Deploy additional monitoring and alerting for service availability and restart procedures
🔍 How to Verify
Check if Vulnerable:
Check NetScaler version against affected versions listed in Citrix advisory CTX677944Check Version:
show version (from NetScaler CLI)Verify Fix Applied:
Verify NetScaler version is updated to patched version and monitor for service stability📡 Detection & Monitoring
Log Indicators:
- Service crash logs
- Unexpected process termination
- High CPU/memory usage spikes
Network Indicators:
- Unusual traffic patterns to NetScaler
- Service unavailability alerts
SIEM Query:
source="netscaler*" AND ("crash" OR "restart" OR "service down")🔗 References
- https://support.citrix.com/article/CTX677944/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20245491-and-cve20245492
- https://support.citrix.com/external/article?articleUrl=CTX677944-netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20245491-and-cve20245492
- https://support.citrix.com/article/CTX677944/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20245491-and-cve20245492
