External risk intelligence

Citrix NetScaler ADC and Gateway Memory Overflow Vulnerability.

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2026-111334

The vulnerability exists in Citrix NetScaler Gateway and ADC, which are network appliances designed by default to act as internet-facing gateways, VPN entry points, and identity portals. These products are intended to be exposed to the public internet to facilitate remote access and traffic management, making them inherently public-facing in normal deployments.

Denial of Service

Halo Surface Signal: 5 out of 5 — more likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A memory overflow vulnerability has been identified in Citrix NetScaler's Endpoint Analysis component, potentially causing disruptions or service interruptions. This issue affects network devices used for secure access and traffic management. The primary concern is to confirm if these specific systems are in use and potentially exposed.

System disruptions from a memory overflow.
Affects network access and traffic management.
Confirm relevance and exposure for leadership.

Attack Path

How an attacker could exploit the issue

An attacker could reach a vulnerability in Citrix NetScaler's Endpoint Analysis component by exploiting network exposure, potentially leading to service disruption. This memory overflow flaw could allow an attacker to cause unpredictable behavior or a denial of service within the affected Citrix products.

No authentication or privileges required.
Network-based trigger of overflow.
Denial of service or erratic behavior.

Live Threat

Current exploitation, exposure, and threat context

A memory overflow in Citrix NetScaler's Endpoint Analysis feature could lead to unpredictable behavior or a denial of service. This could impact the availability and stability of the affected network devices.

Service availability and stability at risk.
Memory overflow when endpoint analysis is used.
Denial of service or erratic behavior.

Operational Fix

Recommended remediation, mitigation, and detection steps

The real-world ownership for this vulnerability likely falls to the infrastructure or platform teams managing Citrix NetScaler ADC and Gateway deployments. Vendor management teams should also be engaged due to the nature of the affected technology. The first practical step is to identify all instances of the affected technology, confirm their exposure and criticality, and then determine the accountable owner for remediation planning.

Infrastructure or Platform teams own remediation.
Verify external reachability and business criticality.
Plan maintenance, coordinate with vendor.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Citrix NetScaler ADC and Gateway?

These are enterprise-grade network appliances designed to manage traffic, balance loads, and provide secure remote access. They serve as gateways and VPN entry points that sit between a company's internal resources and the outside world, ensuring that traffic is efficiently and safely delivered to the correct destination.

How does this CVE-2026-111334 memory overflow affect software?

This vulnerability involves a memory overflow within the Endpoint Analysis component. When a program tries to store more data in a memory buffer than it is designed to hold, the system may become unstable. In this case, it can lead to erratic behavior or a complete denial of service, preventing the appliance from functioning as expected.

Does triggering CVE-2026-111334 require user interaction?

No, an attacker does not need authentication or specific user actions to trigger this flaw. The vulnerability is network-based, meaning it can potentially be reached remotely. Simply accessing the affected Endpoint Analysis feature is the trigger; it does not occur through standard, non-malicious administrative configuration changes.

Is my Citrix appliance at risk according to Halo Surface Signal?

Halo Surface Signal indicates that because these devices are typically deployed as internet-facing gateways to support remote access, they are inherently public-facing. If your Citrix NetScaler ADC or Gateway is accessible via the internet, it falls into the category of high-visibility systems that require immediate attention.

How should I respond to this vulnerability?

Start by identifying all instances of Citrix NetScaler within your infrastructure to determine which are active and business-critical. Once you have an inventory, verify their exposure to the internet and coordinate with your infrastructure or platform teams to prioritize remediation according to vendor-provided guidance.

References

support.citrix.com/support-home/kbsearch/article?articleNumber=CTX697305

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.