CVE-2026-3055: NetScaler ADC/Gateway Info Disclosure Flaw

CVE-2026-3055 Overview

CVE-2026-3055 is a critical out-of-bounds read vulnerability affecting NetScaler ADC and NetScaler Gateway appliances when configured as a SAML Identity Provider (IDP). The vulnerability stems from insufficient input validation during SAML authentication processing, which can lead to memory overread conditions that may expose sensitive data or cause denial of service.

Critical Impact
Unauthenticated remote attackers can exploit this memory overread vulnerability to potentially access sensitive information from memory or disrupt service availability on affected NetScaler appliances configured as SAML IDPs.

Affected Products

NetScaler ADC (when configured as SAML IDP)
NetScaler Gateway (when configured as SAML IDP)
Citrix ADC/Gateway appliances with SAML IDP functionality enabled

Discovery Timeline

2026-03-23 - CVE-2026-3055 published to NVD
2026-03-24 - Last updated in NVD database

Technical Details for CVE-2026-3055

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-bounds Read), indicating that the affected software reads data past the end or before the beginning of the intended buffer. In the context of NetScaler ADC and Gateway SAML IDP implementations, improper validation of input during SAML authentication processing allows attackers to trigger memory read operations beyond allocated buffer boundaries.

The vulnerability is exploitable over the network without requiring authentication or user interaction, making it particularly dangerous for internet-facing NetScaler deployments. When exploited, the memory overread can result in disclosure of sensitive information stored in adjacent memory regions or cause the service to crash, leading to denial of service conditions.

Root Cause

The root cause of CVE-2026-3055 lies in insufficient input validation within the SAML IDP processing logic of NetScaler ADC and Gateway. When handling SAML authentication requests, the appliance fails to properly validate the boundaries of input data, allowing specially crafted requests to read beyond the allocated memory buffer. This out-of-bounds read condition (CWE-125) occurs because the software does not adequately check the length or format of SAML-related input parameters before processing them.

Attack Vector

The attack vector is network-based, requiring the attacker to send malicious SAML authentication requests to the vulnerable NetScaler appliance configured as a SAML IDP. The attack does not require any privileges or user interaction, making it exploitable by unauthenticated remote attackers.

An attacker would craft a malicious SAML request with manipulated parameters designed to trigger the memory overread condition. When the vulnerable NetScaler processes this request, it may read beyond the intended buffer boundaries, potentially exposing sensitive data such as session tokens, cryptographic keys, or other information resident in memory. Additionally, the memory overread could cause the service to crash if it attempts to access invalid memory regions.

Detection Methods for CVE-2026-3055

Indicators of Compromise

Unusual or malformed SAML authentication requests targeting the NetScaler SAML IDP endpoint
Unexpected service crashes or restarts of NetScaler ADC/Gateway services
Anomalous memory access patterns or segmentation faults in NetScaler logs
Network traffic containing abnormally large or malformed SAML assertions

Detection Strategies

Monitor NetScaler system logs for unexpected application crashes or memory-related errors
Implement network intrusion detection rules to identify malformed SAML requests
Deploy web application firewall rules to inspect and validate SAML request structures
Enable verbose logging on SAML IDP endpoints to capture suspicious authentication attempts

Monitoring Recommendations

Configure alerting for NetScaler service availability and unexpected restarts
Establish baseline metrics for SAML authentication traffic patterns and alert on deviations
Monitor memory utilization and error rates on affected NetScaler appliances
Implement real-time log aggregation and analysis for SAML-related events

How to Mitigate CVE-2026-3055

Immediate Actions Required

Review the Citrix Support Article CTX696300 for official guidance
Identify all NetScaler ADC and Gateway appliances configured as SAML IDPs in your environment
Apply available security patches from Citrix as soon as possible
Consider temporarily disabling SAML IDP functionality if patches cannot be immediately applied

Patch Information

Citrix has released security guidance for this vulnerability. Administrators should consult the official Citrix Support Article CTX696300 for detailed patching instructions, affected version information, and updated firmware availability.

Workarounds

Restrict network access to SAML IDP endpoints using firewall rules or access control lists
Implement additional authentication layers or network segmentation to limit exposure
Deploy a web application firewall with SAML request inspection capabilities in front of affected appliances
Monitor for exploitation attempts while preparing to apply official patches

bash

# Example: Restrict access to SAML IDP endpoints via network ACL
# Consult Citrix documentation for NetScaler-specific configuration syntax
# Limit SAML IDP access to trusted IP ranges only
add ns acl SAML_RESTRICT ALLOW -srcIP 10.0.0.0-10.255.255.255 -destPort 443
add ns acl SAML_DENY DENY -destPort 443
apply ns acls