CVE-2025-6543criticalunder attackCWE-119

CVE-2025-6543: critical vulnerability in NetScaler ADC

Memory overflow vulnerability leading to unintended control flow and Denial of Service

Published · Updated

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83Vexday Risk Score

Prioritize patching. It under exploitation confirmed by CISA, has an official Brazilian government alert and has a public proof of concept.

ssvc Actcvss 9.2epss 10%
from disclosure to weapon1 day
Published on NVDJun 25
1st PoC+1d
CISA KEV+5d
Official alert in Brazil

Brazil's federal government published an alert, recommendation or bulletin that cites this vulnerability.

  • CTIR Gov · ALERTA 10/2025Vulnerabilidades nos produtos (Citrix) NetScaler ADC e NetScaler Gatewayread on gov.br ↗
Source: CTIR Gov (GSI) and CISC Gov.br, under the CC BY-ND 3.0 license.
Action required by CISAfederal deadline: 2025-07-21

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

In short

A memory overflow flaw in NetScaler ADC and Gateway products allows attackers to crash the system or gain unauthorized control when these devices are configured as VPN gateways or authentication servers. This is a critical issue that can disrupt network access for many users.

Technical detail

A stack or heap buffer overflow vulnerability in NetScaler ADC/Gateway exists when configured as a VPN virtual server, ICA Proxy, CVPN, RDP Proxy, or AAA virtual server. The vulnerability enables remote attackers to trigger unintended control flow, resulting in denial of service or potential code execution. No authentication is required to trigger the condition.

Summary generated and translated by AI from the official description.

The full analysis of this CVE is available in Portuguese →

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:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L
Affected products
NetScaler · ADCNetScaler · Gateway
⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
Related CVEs — NetScaler ADC

In the same product, most dangerous first.

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