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CVE-2025-6543

Citrix NetScaler ADC and Gateway Buffer Overflow

9.8 CRITICALActively exploited (CISA KEV)EPSS 10.6%
  1. Published25 Jun 2025
  2. Added to CISA KEV30 Jun 2025
  3. Remediation due21 Jul 2025
Actively exploited (CISA KEV)

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.

Added to KEV: 30 Jun 2025Federal remediation due: 21 Jul 2025

Description

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

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Citrix NetScaler Application Delivery Controller≥ 13.1 < 13.1-59.19 · ≥ 14.1 < 14.1-47.46 · ≥ 13.1 < 13.1-37.236
Citrix NetScaler Gateway≥ 13.1 < 13.1-59.19 · ≥ 14.1 < 14.1-47.46

Remediation

Fixed in
Citrix NetScaler Application Delivery Controller≥ 13.1-59.19
Citrix NetScaler Gateway≥ 13.1-59.19

References

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Frequently asked

Is CVE-2025-6543 being actively exploited?

Yes. CVE-2025-6543 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 30 Jun 2025.

How severe is CVE-2025-6543?

CVE-2025-6543 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 10.6% probability of exploitation.

Which products are affected by CVE-2025-6543?

Affected products include Citrix NetScaler Application Delivery Controller, Citrix NetScaler Gateway.

How do I fix CVE-2025-6543?

Upgrade affected software to a fixed version, for example Citrix NetScaler Application Delivery Controller 13.1-59.19, Citrix NetScaler Gateway 13.1-59.19 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2025-6543 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, a risk for it never ranks below high, and the update that fixes it moves to the Emergency patch lane. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.