---
id: "CVE-2025-6543"
kind: "vulnerability"
aliases: ["CVE-2025-6543"]
title: "Memory overflow vulnerability leading to unintended control flow and Denial of Service in NetScaler ADC and\u2026"
severity: "critical"
cvss: 9.8
epss: null
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Citrix NetScaler ADC and Gateway", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "citrix netscaler application delivery controller", "fixed": ["13.1-37.236"], "affected": ">= 13.1, < 13.1-37.236", "ecosystem": "vendor"}, {"name": "citrix netscaler application delivery controller", "fixed": ["13.1-59.19"], "affected": ">= 13.1, < 13.1-59.19", "ecosystem": "vendor"}, {"name": "citrix netscaler application delivery controller", "fixed": ["14.1-47.46"], "affected": ">= 14.1, < 14.1-47.46", "ecosystem": "vendor"}, {"name": "citrix netscaler gateway", "fixed": ["13.1-59.19"], "affected": ">= 13.1, < 13.1-59.19", "ecosystem": "vendor"}, {"name": "citrix netscaler gateway", "fixed": ["14.1-47.46"], "affected": ">= 14.1, < 14.1-47.46", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["citrix", "exploited", "gateway", "infrastructure", "netscaler", "vpn"]
not_affected_if: ["not-gateway-or-aaa-config"]
published_at: "2025-06-25T13:15:27+00:00"
first_seen_at: "2026-10-23T19:11:51+00:00"
updated_at: "2026-10-23T22:29:05+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2025-6543", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-6543", "first_seen_at": "2026-10-23T22:29:05+00:00"}]
---

# Memory overflow vulnerability leading to unintended control flow and Denial of Service in NetScaler ADC and…

A buffer overflow in Citrix NetScaler ADC and Gateway can be triggered to redirect control flow or crash the appliance. CISA lists it as actively exploited in the wild.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Citrix NetScaler ADC and Gateway affected ? fixed ?
- vendor:citrix netscaler application delivery controller affected >= 13.1, < 13.1-37.236 fixed 13.1-37.236
- vendor:citrix netscaler application delivery controller affected >= 13.1, < 13.1-59.19 fixed 13.1-59.19
- vendor:citrix netscaler application delivery controller affected >= 14.1, < 14.1-47.46 fixed 14.1-47.46
- vendor:citrix netscaler gateway affected >= 13.1, < 13.1-59.19 fixed 13.1-59.19
- vendor:citrix netscaler gateway affected >= 14.1, < 14.1-47.46 fixed 14.1-47.46

## How to check

Check whether NetScaler is configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server; the sources do not give a command.

## Fix

Apply the mitigations and fixed build from Citrix's vendor advisory; the sources do not name the fixed version.
If no mitigation is available, discontinue use of the product per CISA guidance.

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2025-6543
- 2026-10-23T22:29:05+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2025-6543

## From the sources

Citrix NetScaler ADC and Gateway contain a buffer overflow vulnerability leading to unintended control flow and Denial of Service. NetScaler must be configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server.

CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_