CVE-2026-88776 in ADC
Summary
by MITRE • 09/27/2026
Memory overflow vulnerability 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 unpredictable or erroneous behavior or Denial of Service
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Analysis
by VulDB Data Team • 09/27/2026
The identified vulnerability represents a critical memory overflow condition within the core architecture of Citrix NetScaler ADC and Citrix NetScaler Gateway appliances. This flaw is present in specific legacy versions, including all releases prior to 14.1-73.37 and 13.1-64.23 for both ADC and Gateway platforms, as well as FIPS-compliant variants before version 14.1-73.37 and NDcPP certified builds before 13.1.37.279. The root cause lies in the improper handling of memory allocation or buffer boundaries during specific processing operations within the appliance software stack. When an attacker triggers this condition, typically through crafted network traffic or malformed input data directed at the management interface or application delivery services, the system fails to correctly validate the size of incoming data against allocated buffers. This lack of boundary checking results in writing data beyond the intended memory limits, corrupting adjacent memory structures and leading to undefined behavior within the operating environment.
From a technical perspective, this vulnerability aligns with CWE-120, which classifies buffer copy without checking size limitations, often resulting in heap or stack-based overflows depending on where the vulnerable code resides within the NetScaler firmware. The exploitation of this flaw does not necessarily require authentication if it targets exposed services such as HTTP/HTTPS endpoints or specific API interfaces managed by the ADC/Gateway engine. Once triggered, the memory corruption can destabilize critical system processes responsible for session management, routing decisions, and SSL termination. This instability manifests as unpredictable application behavior, where legitimate user sessions may be dropped, configuration states become inconsistent, or service responses return erroneous data to clients attempting to access hosted applications.
The operational impact of this vulnerability is severe, primarily centering on the availability component of the CIA triad due to its potential to cause a Denial of Service condition. By repeatedly triggering the memory overflow, an attacker can exhaust system resources such as RAM or CPU cycles allocated for handling these malformed requests, effectively rendering the NetScaler appliance unresponsive. In high-availability deployments where this device serves as a critical load balancer and secure access gateway, such instability can lead to widespread service outages across multiple backend applications protected by the Citrix infrastructure. Furthermore, while the primary reported impact is denial of service, memory corruption vulnerabilities inherently carry risks related to code execution if an attacker can precisely control the overwritten memory contents to redirect program flow, although this specific advisory emphasizes availability impacts over remote code execution capabilities.
To mitigate this risk, organizations must prioritize immediate patching by upgrading Citrix NetScaler ADC and Gateway appliances to version 14.1-73.37 or later for non-FIPS deployments, and version 13.1-64.23 or later for standard releases. For environments requiring FIPS compliance, the upgrade target is specifically version 14.1-73.37 FIPS, while NDcPP certified systems must be updated to at least 13.1.37.279 NDcPP. Until patches are applied, network-level mitigations should be implemented by restricting access to the NetScaler management interface and exposed service ports using strict firewall rules or Access Control Lists that limit source IP addresses to trusted administrative ranges only. Additionally, deploying Web Application Firewalls with signatures capable of detecting buffer overflow patterns can provide a layer of defense against exploitation attempts targeting these specific software versions. Continuous monitoring for anomalous traffic spikes or system resource exhaustion alerts is also recommended to detect potential exploitation activities in real-time.