Known exploited vulnerability
CVE-2025-6543
The short answer
CVE-2025-6543 affects NetScaler ADC and is rated critical (CVSS 9.2). CISA added it to the Known Exploited Vulnerabilities catalog on 2025-06-30: attackers are using it, so patch it first.
What it is
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
Weakness: CWE-119.
Severity
9.2 critical
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Exploited (CISA KEV)
Yes, since Jun 30, 2025
Federal due date Jul 21, 2025
EPSS, next 30 days
10%
Higher than 96% of scored CVEs
How it can be exploited
- Attack vector
- Network
- Attack complexity
- High
- Attack requirements
- Present
- Privileges required
- None
- User interaction
- None
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
What CISA says to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Affected products
ADC, Gateway. NVD's record lists the exact affected versions.
References
- support.citrix.com/support-home/kbsearch/article?articleNumber=CTX694788 Vendor Advisory
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-6543 US Government Resource
Questions
Is CVE-2025-6543 being exploited?
Yes. CISA added CVE-2025-6543 to its Known Exploited Vulnerabilities catalog on 2025-06-30, with a federal remediation due date of 2025-07-21.
How do I fix CVE-2025-6543?
CISA's required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
From NVD, CISA KEV, FIRST EPSS and OSV.dev, checked . Status on NVD: Analyzed. The description is NVD's text, quoted as published.
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