Critical Flaw Discovered in the Cisco’s SSL VPN Solution

Adaptive Security Appliance

Cisco warns of a critical flaw in its SSL VPN solution, Adaptive Security Appliance software (ASA) which could allow remote attackers to obtain full control of the system.

The vulnerability is located in the Secure Sockets Layer (SSL) VPN functionality of the Cisco Adaptive Security Appliance (ASA) Software which could allow unauthenticated, remote attacker to cause a reload of the affected system or to remotely execute code.

Security researcher  Cedric Halbronn, NCC Group, discovered the vulnerability and reported it to Cisco.

According to the security advisory published by Cisco “The vulnerability is due to an attempt to double free a region of memory when the webvpn feature is enabled on the Cisco ASA device. An attacker could exploit this vulnerability by sending multiple, crafted XML packets to a webvpn-configured interface on the affected system. An exploit could allow the attacker to execute arbitrary code and obtain full control of the system, or cause a reload of the affected device”.

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The vulnerability only affects ASA devices where the webvpn feature is enabled. Admin can check whether the webvpn feature is enabled or not by using the show running-config webvpn command at the CLI.

The bug also affects the FTD 6.2.2 software released in September which was the first to support remote access VPN feature.

Cisco said that the Product Security Incident Response Team (PSIRT) is aware of the vulnerability and till now there was no reports of any malicious use of the vulnerability. The company has also released a software update that addresses the vulnerability.

The vulnerability was classified as critical and was rated the highest severity of 10.0 on CVSS. Cisco has provided instruction to admins regarding the vulnerability which can be seen here.

List of products which are affected by this vulnerability are given below:

  • 3000 Series Industrial Security Appliance (ISA)
  • ASA 5500 Series Adaptive Security Appliances
  • ASA 5500-X Series Next-Generation Firewalls
  • ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers
  • ASA 1000V Cloud Firewall
  • Adaptive Security Virtual Appliance (ASAv)
  • Firepower 2100 Series Security Appliance
  • Firepower 4110 Security Appliance
  • Firepower 9300 ASA Security Module
  • Firepower Threat Defense Software (FTD)

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