CVE-2026-88774 in ADC
Summary
by MITRE • 09/27/2026
Vulnerability in Citrix NetScaler ADC and Citrix NetScaler Gateway.
This issue affects ADC: before 14.1-73.37, before 13.1-64.23, before 14.1-73.37 FIPS, and before 13.1.37.279 FIPS and NDcPP; Gateway: before 14.1-73.37 and before 13.1-64.23 leading to a feature policy bypass due to improper HTTP URL based expression usage.
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Analysis
by VulDB Data Team • 09/27/2026
The identified vulnerability resides within the core access control mechanisms of Citrix NetScaler ADC and Citrix NetScaler Gateway, specifically affecting versions prior to 14.1-73.37, 13.1-64.23, and their respective FIPS and NDcPP compliant builds such as 13.1.37.279. This security flaw is classified under CWE-862, which denotes a Missing Authorization check, but more specifically it manifests as an improper implementation of access control policies driven by HTTP URL-based expressions. The architecture of NetScaler relies heavily on policy expressions to determine whether incoming requests should be allowed or denied based on attributes such as the Uniform Resource Identifier path, query parameters, and headers. In this instance, the logic governing these expressions fails to correctly validate or sanitize inputs in a manner that prevents unauthorized traversal or bypassing of defined security boundaries.
The technical root cause involves how the appliance processes HTTP URL-based policy conditions during request evaluation. When an administrator configures access policies using regular expressions or string matching against URLs, the underlying engine exhibits a flaw where certain crafted sequences can evade detection rules intended to block malicious paths or unauthorized endpoints. This allows attackers to construct specific HTTP requests that appear benign according to the flawed expression logic but effectively bypass the configured security filters. The vulnerability essentially creates a gap between the intended policy configuration and its actual enforcement at runtime, enabling an unauthenticated attacker to access protected resources or administrative interfaces without proper credentials.
From an operational perspective, this feature policy bypass poses a severe risk to organizational infrastructure integrity. An adversary exploiting this flaw could gain unauthorized access to sensitive internal applications hosted behind the NetScaler appliance, potentially leading to data exfiltration, credential theft, or further lateral movement within the network. Given that Citrix ADC and Gateway often serve as the primary entry point for remote users accessing corporate resources via Secure Web Gateway (SWG) or Virtual Desktop Infrastructure (VDI), compromising this component can result in a complete breach of perimeter security. The impact is particularly critical because it affects both standard deployments and those operating under strict compliance frameworks like FIPS 140-2/3 and NDcPP, where maintaining rigorous access control integrity is mandatory for regulatory adherence.
This vulnerability aligns with the MITRE ATT&CK technique T1190, which describes Exploit Public-Facing Application attacks, as it leverages a flaw in an externally accessible service to bypass authentication or authorization controls. Furthermore, it relates to CWE-284 Improper Access Control and CWE-755 Failure to Handle Exceptional Conditions if the bypass is triggered by unexpected input formats that crash standard validation routines while allowing malicious payloads through. The exploitation does not require complex pre-authentication steps beyond crafting a specific HTTP request, making it highly accessible for automated scanning tools and opportunistic attackers targeting known vulnerable versions.
To mitigate this risk, organizations must immediately apply the vendor-provided patches to upgrade NetScaler ADC and Gateway to version 14.1-73.37 or later, or 13.1-64.23 or later for legacy support lines. It is imperative that administrators verify their current build numbers against the affected list provided by Citrix, including specific FIPS and NDcPP variants which have distinct versioning schemes such as 13.1.37.279. In environments where immediate patching is not feasible due to operational constraints, temporary mitigations should include implementing strict Web Application Firewall (WAF) rules that inspect URL patterns more rigorously than the native policy engine, or restricting network access to these appliances via IP allow-lists if they are exposed to untrusted networks. Regular auditing of access policies and continuous monitoring for anomalous HTTP requests targeting sensitive endpoints can also help detect potential exploitation attempts in real-time.