Patch your Cisco firewall now unless your company has no secrets

Researchers have uncovered a critical security flaw in devices running Cisco’s ASA software that opens a door for any hacker on the internet to penetrate corporate networks.

Cisco has issued a high severity alert to customers using devices in its ASA Adaptive Security Appliance family to patch a remotely exploitable bug that can be triggered by sending ASA routers tailored packets over the internet.

The bug was reported by David Barksdale, Jordan Gruskovnjak, and Alex Wheeler, researchers at US security firm Exodus Intelligence.

Cisco customers should apply its update given that the security firm has now published a detailed analysis of the bug and how it can be exploited.

The buffer overflow bug affects Internet Exchange Key (IKE), a highly sensitive cryptographic component of Cisco’s ASA routers that serve as the corporate firewall, network antivirus, intrusion prevention system, and virtual private network.

IKE is used to establish an encrypted connection and handles functions such as authentication, IPSec tunnelling and key exchange.

The bug affects several ASA devices, however the researchers note that it only affects devices configured as a virtual private network (VPN)

“When deployed as a VPN, the device is accessible from the Internet and provides access to a company’s internal networks,” the researchers wrote.

Cisco said the bug affects versions 1 and 2 of IKE and “could allow an unauthenticated, remote attacker to cause a reload of the affected system or to remotely execute code.”

“An attacker could exploit this vulnerability by sending crafted UDP packets to the affected system,” it added.

“An exploit could allow the attacker to execute arbitrary code and obtain full control of the system or to cause a reload of the affected system.”

Affected devices include Cisco’s 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 9300 ASA Security Module; and ISA 3000 Industrial Security Appliance.

According to Cisco, affected VPN configurations include LAN-to-LAN IPsec VPN; Remote access VPN using the IPsec VPN client; Layer 2 Tunneling Protocol (L2TP)-over-IPsec VPN connections; and IKEv2 AnyConnect.

Read more: ​Re-used crypto keys expose millions of devices to attack

“To determine whether the Cisco ASA is configured to terminate IKEv1 or IKEv2 VPN connections, a crypto map must be configured for at least one interface. Administrators should use the show running-config crypto map | include interface command and verify that it returns output,” Cisco said.

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Tags ASA softwarecryptographicInternet Exchange Key (IKE)ASA Adaptive Security Applianceciscovulnerability

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