Exploited

CVE-2025-6543

Citrix NetScaler ADC / Gateway · Load balancers and access gateways (ADC)

Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability

At a glance

Exploited. Added to CISA’s catalog of exploited vulnerabilities on June 30, 2025.

Affected product: Citrix NetScaler ADC / Gateway (category Load balancers and access gateways (ADC), indicative classification). Name in CISA’s catalog: Citrix NetScaler ADC and Gateway.

What should I do?

Apply the patches or mitigations from Citrix; if none are available, stop using the product. For cloud services, follow the guidance from Citrix.

Deadline set by CISA for US federal agencies: 21 days (due July 21, 2025). It only binds those agencies, but it is a useful measure of urgency.

Citrix security advisories page (general page, not the advisory for this vulnerability)
The vendor’s specific advisory is listed in the NVD references: CVE-2025-6543 on the NVD website.

Original text of the required action (CISA)

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

Timeline

June 25, 2025 Vulnerability published Publication date (NVD)
June 30, 2025 Exploitation confirmed Added to CISA’s KEV catalog
July 21, 2025 CISA deadline Remediation deadline set for US federal agencies

The facts, with their sources

Exploitation confirmed: Yes, on June 30, 2025 Date added to the catalog of exploited vulnerabilities. Exploitation itself may have started earlier. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Ransomware: No known use to date That does not guarantee it is not being used: the information is not public. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Hunt for compromise: Not requested by CISA Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CISA required action: Apply the patches or mitigations from Citrix; if none are available, stop using the product. For cloud services, follow the guidance from Citrix. Rewritten by this site from CISA’s original text. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CISA deadline: July 21, 2025, 21 days Set for US federal agencies: a measure of urgency, not an obligation elsewhere. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Vulnerability published: June 25, 2025 Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
Product according to CISA: Citrix NetScaler ADC and Gateway Filed by this site under “Load balancers and access gateways (ADC)” (indicative classification). Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Technical detail of the score: attack vector, complexity, impact. Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC

Severity and activity

9.8 / 10 CVSS severity: critical

Score from the NVD. Collected Sep 29, 2026.

— Probability of exploitation in the next 30 days (EPSS)

FIRST’s EPSS model. Since exploitation is already confirmed, this figure is mostly useful to compare activity. Collected Sep 29, 2026.

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

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.

Summary from CISA (KEV catalog).

CERT-FR advisories

CERTFR-2025-ALE-009: Multiples vulnérabilités dans Citrix NetScaler ADC et NetScaler Gateway (updated August 18, 2025)

Information reused under the Open Licence 2.0 (Etalab); the date of last update is shown for each advisory. This site is neither affiliated with nor endorsed by ANSSI.

Sources for this page

CISA KEV catalog: exploitation, date added, required action, deadline, ransomware.
NVD (NIST): CVSS severity, publication date, description, vendor references.
EPSS (FIRST): probability of exploitation.
CERT-FR: advisories and alerts (in French).
Brand and category: indicative classification by this site (method).