Networking equipment vendor Cisco said today that some of its security products fail to detect and stop traffic to malicious servers that abuse a technique called SNIcat to covertly steal data from inside corporate networks.

A vulnerability in Server Name Identification (SNI) request filtering of Cisco Web Security Appliance (WSA), Cisco Firepower Threat Defense (FTD), and the Snort detection engine could allow an unauthenticated, remote attacker to bypass filtering technology on an affected device and exfiltrate data from a compromised host.

This vulnerability is due to inadequate filtering of the SSL handshake. An attacker could exploit this vulnerability by using data from the SSL client hello packet to communicate with an external server. A successful exploit could allow the attacker to execute a command-and-control attack on a compromised host and perform additional data exfiltration attacks.

Cisco became the fourth major network security vendor after F5 Networks, Fortinet, and Palo Alto Networks to formally admit that its devices can be bypassed using the SNIcat technique. Surprisingly Checkpoint is not vulnerable to the attack technique

Affected products

  • CISCO 3000 Series Industrial Security Appliances (ISAs)
  • CISCO FTD Software
  • CISCO WSA Software

Potentially Affected

  • 1000 Series Integrated Services Routers (ISRs)
  • 4000 Series ISRs
  • Catalyst 8000V Edge Software
  • Catalyst 8200 Series Edge Platforms
  • Catalyst 8300 Series Edge Platforms
  • Catalyst 8500L Edge Platforms
  • Cloud Services Router 1000V Series (CSR 1000V)
  • Integrated Services Virtual Router (ISRv)
  • Meraki Security Appliances, all models

Currently no patch available for the vulnerability, The Cisco Product Security Incident Response Team (PSIRT) is aware that proof-of-concept exploit code is available for the vulnerability described in this advisory. The Cisco PSIRT is not aware of any malicious use of the vulnerability that is described in this advisory.