Netscaler Application Delivery ControllerApplication · Citrix

CVE-2025-6543

CRITICAL · 9.8 CVSS v3.1 Published 2025-06-25

Fix available

A fix is available. Upgrade to 13.1-37.236 / 13.1-59.19 or later.

See remediation →

100/100

Remediation priority · Urgent

In the wild Remotely reachable No privileges Zero-click

Official description

NVD · unedited

Memory overflow vulnerability leading to unintended control flow and Denial of Service in NetScaler ADC and NetScaler Gateway when configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server

Technical summary

dbcve analysis · moderate confidence

A memory overflow vulnerability in Citrix NetScaler ADC and NetScaler Gateway allows attackers to cause unintended control flow and denial of service when the appliance is configured as a Gateway (supporting VPN virtual server, ICA Proxy, CVPN, or RDP Proxy) or an AAA virtual server. The critical CVSS 9.8 suggests potential for remote code execution.

MitigationApply the vendor-released patch or upgrade to a supported NetScaler ADC/Gateway version that addresses this vulnerability. Review and harden Gateway and AAA virtual server configurations if immediate patching is not feasible.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions

NVD · CPE data

Netscaler Application Delivery ControllerApplication

Affected:>= 13.1, < 13.1-37.236>= 13.1, < 13.1-59.19>= 14.1, < 14.1-47.46

Netscaler GatewayApplication

Affected:>= 13.1, < 13.1-59.19>= 14.1, < 14.1-47.46

CVSS breakdown

From the vector

Attack vector: Network
Complexity: Low
Privileges: None
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected?

dbcve checks

Work through these to decide whether this CVE applies to you.

Identify NetScaler product type and version

Run `show version` on the NetScaler command line or check the GUI under System > Information > Version. Note whether it is NetScaler ADC or NetScaler Gateway.

Affected if The installed version is 13.1 build 37.235 or lower, 13.1 build 59.18 or lower, or 14.1 build 47.45 or lower.
Verify Gateway virtual server configuration

Run `show vpn vserver` to list all VPN virtual servers. Check for configured virtual servers with VPN, ICA Proxy, CVPN, or RDP Proxy type enabled.

Affected if Any VPN virtual server, ICA Proxy, CVPN, or RDP Proxy is actively configured on the device.
Verify AAA virtual server configuration

Run `show aaa vserver` to list all AAA virtual servers. Check for any actively configured AAA virtual servers.

Affected if Any AAA virtual server is configured on the device.
Confirm the device is exposed to untrusted networks

Review the bound IP address and access control lists for the Gateway or AAA virtual servers identified in previous steps. Check `show run` output for interface bindings.

Affected if The Gateway or AAA virtual server is bound to a publicly accessible IP address or accepts connections from untrusted networks.

The environment is affected if the NetScaler runs a vulnerable version (13.1 before build 59.19 or 14.1 before build 47.46) AND has a Gateway virtual server (VPN, ICA Proxy, CVPN, or RDP Proxy) or AAA virtual server configured and exposed.

Generated from the published advisory. Verify against your own configuration.

Remediation

dbcve · scoped

Upgrade available Upgrade to 13.1-37.236 / 13.1-59.19 / 14.1-47.46 or later

Fixed in 13.1-37.23613.1-59.1914.1-47.46

Interim mitigation

Apply the vendor-released patch or upgrade to a supported NetScaler ADC/Gateway version that addresses this vulnerability. Review and harden Gateway and AAA virtual server configurations if immediate patching is not feasible.

Recommended fix High confidence

Upgrade to NetScaler 13.1-59.19 or later, or 14.1-47.46 or later

1. Identify the current NetScaler ADC or Gateway version by running 'show version' or checking the GUI dashboard
2. Confirm the deployment uses Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server configuration, as only these configurations are affected
3. Schedule a maintenance window as the upgrade will require a brief service interruption
4. Download the appropriate build from Citrix support: version 13.1-59.19 or later for 13.1 releases, or version 14.1-47.46 or later for 14.1 releases
5. Back up the current NetScaler configuration using 'save ns config' and export the ns.conf file
6. Upload the new firmware build via the NetScaler GUI (System > Firmware) or CLI
7. Install the firmware and restart the NetScaler device
8. After reboot, verify the new version is running with 'show version'

Caveat Standard NetScaler firmware upgrade; review Citrix release notes for any configuration changes required for the specific target version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Netscaler Application Delivery Controller Exploited in the wild — priority engagement

Consultation4.0 h
Implementation8.0 h
Testing6.0 h
Review / QA3.0 h

21.0 hours of engineering $3,680

Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,888.

Scan for this in your stack

Free · runs locally

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References

Primary sources

support.citrix.comVendor Advisory
www.cisa.govUS Government Resource
nvd.nist.govNVD record

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-6543 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2025-6543?

The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.

The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here

Verified mitigations, workarounds, and config changes
Version or environment caveats, and links to real fixes
No weaponised exploit code, or anything meant to cause harm
No spam, self-promotion, credentials, or personal data

At a glance

Exploited in the wildOn CISA’s known-exploited list · agencies must fix by 2025-07-21

A fix existsUpgrade to 13.1-37.236 / 13.1-59.19 or later

Severity 9.8 Critical

Exploit likelihood EPSS, next 30 days 10.1%

Affects: Netscaler Application Delivery Controller

Remediation

Being exploited — close it fast

Fix this in Netscaler Application Delivery Controller 21 hrs · Moderate

Typical engagement from $3,680

Get it fixed fast See the full breakdown ↓

This CVE is on CISA’s actively-exploited list, so the clock is real — a vetted specialist can deliver a reviewed fix for your staging environment quickly.

You’ll deal with our team directly and deploy the reviewed fix to staging first — never straight to production.

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

Check your environment

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

Scan for this in your stack

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Practitioner notes

No notes yet

Official description

Technical summary

Affected products & versions

CVSS breakdown

Am I affected?

Remediation

References