US, Australia warn of latest Citrix security flaw after NetScaler advisory

What happened

Citrix confirmed late on Friday that it was “tracking a newly observed issue” related to some customer-managed NetScaler deployments but claimed the problem was not connected to vulnerabilities reported last week that also caused alarm among cybersecurity experts. Customers began reporting strange exploitation incidents on Friday, even on appliances that were up to date on all patches.

The vulnerability carries a severity score of 8.7 out of 10 and Citrix confirmed that it saw “targeted attacks on unmitigated NetScaler deployments which can lead to Denial of Service.” On Sunday, the Cybersecurity and Infrastructure Security Agency (CISA) ordered all federal agencies to patch the bug by Wednesday and conduct forensic triage.

Citrix NetScaler application delivery controllers (ADC) and Gateway devices are used by large organizations to manage traffic and authentication. “If the condition is triggered repeatedly, the service may remain unavailable,” Citrix said.