NetScaler LoadBalancer Archive

Checklist for NetScaler (Citrix ADC) CVE-2023-3519

Citrix issued an alert yesterday (07/18/2023) about a critical vulnerability (CVE-2023-3519) in all NetScaler (Citrix ADC) & Gateway systems. To date, no working exploits have been published.

Important ! There are no patches for NetScaler (Citrix ADC) version 12.1 or older. These systems have reached their EOL and will therefore no longer be equipped with the necessary fix. In this case please update to the latest 13.0 or 13.1 version.

The vulnerability allows anonymous remote code execution and thus unauthenticated attackers to take over various machines with root privileges.

As we hear from the Citrix community, more and more attacked systems are being found. The first exploits have also been available for purchase on the dark web for some time.

Web Authentication Action in NetScaler

On one of my recent deployments, I needed to set up external access using NetScaler to an internally hosted web application (Grafana).

Grafana is a cross-platform open source application for graphical representation of data from various data sources such as InfluxDB, MySQL, PostgreeSQL, Prometheus and Graphite.

The challenge here was that the customer wanted to pre-install authentication on the NetScaler, but the users were only known to the web application itself.

The question that therefore came to me was:
How can I check the user of the web application if only the web application itself has access to the user data?

I had only used standards like LDAP, RADIUS, CERT, SAML etc. for user authentication on NetScaler, but these were not useful here because the target system should not be changed.

Checklist for Citrix ADC CVE-2019-19781

Citrix has released a critical vulnerability warning (CVE-2019-19781) in all Citrix ADC & Gateway systems one week before Christmas. Several working exploits have been released since Jan. 10, 2020 and are available to everyone.

Important ! The fix from Citrix with the Responder Policy does not work on systems with version 12.1.51.16/51.19, 50.31 and older. If this version is in use, please update to the latest 12.1 version.

The exploits allow remote code to be executed anonymously, allowing unauthenticated attackers to take over the various machines with root privileges.