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CVE-2025-6543: Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability

criticalknown exploitedpublic exploitCVE-2025-6543
Actively exploited. At least one CVE in this advisory is listed in the CISA Known Exploited Vulnerabilities catalog — exploitation has been observed in the wild. Treat remediation as urgent.
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.

CSIRTS triage

vendor: Citrixproduct: NetScaler ADC and GatewayDenial of service
What
This vulnerability is a buffer overflow leading to denial of service.
Who is affected
Deployments of Citrix NetScaler ADC and Gateway configured as specified are affected.
Urgency
Remediation is critical due to active exploitation and the severity of the vulnerability.
Action
Apply the latest security updates from Citrix.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source
CISA Known Exploited Vulnerabilities (US · database · site)
Severity
critical
Published
2025-06-30
Exploitation
Observed in the wild (CISA KEV)

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2025-6543

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2025-6543coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Citrix NetScaler ADC

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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