---
id: "CVE-2023-6549"
kind: "vulnerability"
aliases: ["CVE-2023-6549"]
title: "Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway\u2026"
severity: "high"
cvss: 8.2
epss: null
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Citrix NetScaler ADC and NetScaler Gateway", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "citrix netscaler application delivery controller", "fixed": ["12.1-55.302"], "affected": ">= 12.1, < 12.1-55.302", "ecosystem": "vendor"}, {"name": "citrix netscaler application delivery controller", "fixed": ["13.0-92.21"], "affected": ">= 13.0, < 13.0-92.21", "ecosystem": "vendor"}, {"name": "citrix netscaler application delivery controller", "fixed": ["13.1-37.176"], "affected": ">= 13.1, < 13.1-37.176", "ecosystem": "vendor"}, {"name": "citrix netscaler application delivery controller", "fixed": ["13.1-51.15"], "affected": ">= 13.1, < 13.1-51.15", "ecosystem": "vendor"}, {"name": "citrix netscaler application delivery controller", "fixed": ["14.1-12.35"], "affected": ">= 14.1, < 14.1-12.35", "ecosystem": "vendor"}, {"name": "citrix netscaler gateway", "fixed": ["13.0-92.21"], "affected": ">= 13.0, < 13.0-92.21", "ecosystem": "vendor"}, {"name": "citrix netscaler gateway", "fixed": ["13.1-51.15"], "affected": ">= 13.1, < 13.1-51.15", "ecosystem": "vendor"}, {"name": "citrix netscaler gateway", "fixed": ["14.1-12.35"], "affected": ">= 14.1, < 14.1-12.35", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["citrix", "exploited", "infrastructure", "netscaler", "self-hosted", "vpn-gateway"]
not_affected_if: ["default-config"]
published_at: "2024-01-17T00:00:00+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-2023-6549", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-6549", "first_seen_at": "2026-10-23T22:29:05+00:00"}]
---

# Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway…

Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow that lets an attacker crash the appliance, causing denial of service. 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 NetScaler Gateway affected ? fixed ?
- vendor:citrix netscaler application delivery controller affected >= 12.1, < 12.1-55.302 fixed 12.1-55.302
- vendor:citrix netscaler application delivery controller affected >= 13.0, < 13.0-92.21 fixed 13.0-92.21
- vendor:citrix netscaler application delivery controller affected >= 13.1, < 13.1-37.176 fixed 13.1-37.176
- vendor:citrix netscaler application delivery controller affected >= 13.1, < 13.1-51.15 fixed 13.1-51.15
- vendor:citrix netscaler application delivery controller affected >= 14.1, < 14.1-12.35 fixed 14.1-12.35
- vendor:citrix netscaler gateway affected >= 13.0, < 13.0-92.21 fixed 13.0-92.21
- vendor:citrix netscaler gateway affected >= 13.1, < 13.1-51.15 fixed 13.1-51.15
- vendor:citrix netscaler gateway affected >= 14.1, < 14.1-12.35 fixed 14.1-12.35

## Fix

Apply the mitigation or fixed build from Citrix's advisory for CVE-2023-6549; if none is available, discontinue use of the product as CISA directs.

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2023-6549
- 2026-10-23T22:29:05+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2023-6549

## From the sources

Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow vulnerability that allows for a denial-of-service when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.

CISA required action: Apply mitigations per vendor instructions 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_