Critical VPN key exchange flaw exposes Cisco security appliances to remote hacking

Firewalls running Cisco Adaptive Security Appliance (ASA) software can be compromised remotely with malformed UDP packets

Cisco Systems patched a critical vulnerability that could allow remote attackers to take over Cisco Adaptive Security Appliance (ASA) firewalls configured as virtual private network servers by simply sending malformed network packets to them.

For devices that are designed to protect private networks from Internet attacks, this is as bad as it gets. That's why Cisco rated the vulnerability with the maximum score of 10 in the Common Vulnerability Scoring System.

The flaw is located in the Cisco ASA code that handles the Internet Key Exchange version 1 (IKEv1) and IKE version 2 (IKEv2) protocols. More precisely, it stems from a buffer overflow condition in the function that processes fragmented IKE payloads.

"An attacker could exploit this vulnerability by sending crafted UDP packets to the affected system," Cisco said in an advisory. "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."

IKE is used as a key exchange mechanism in IPsec-based virtual private networks (VPNs). As such, the Cisco ASA devices are only vulnerable if they are configured to act as termination points for 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.

Cisco ASA products are frequently configured for VPN. Their strength is that they can provide IP routing, firewall, network antivirus, intrusion prevention and VPN functionality in a single device.

According to Cisco the following products are vulnerable: Cisco ASA 5500 Series Adaptive Security Appliances, Cisco ASA 5500-X Series Next-Generation Firewalls, Cisco ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers, Cisco ASA 1000V Cloud Firewall, Cisco Adaptive Security Virtual Appliance (ASAv), Cisco Firepower 9300 ASA Security Module and Cisco ISA 3000 Industrial Security Appliance.

The Cisco advisory contains a list with the fixed Cisco ASA software versions for different release branches. Users are advised to update as soon as possible.

The Internet Storm Center at the SANS Technology Institute has reported seeing a large increase in Internet probes on UDP port 500, which is the most likely port number for exploiting this vulnerability.

Join the newsletter!

Error: Please check your email address.
Rocket to Success - Your 10 Tips for Smarter ERP System Selection
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Lucian Constantin

IDG News Service
Show Comments

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Ratchada Dunn

Sharp PN-40TC1 Huddle Board

The Huddle Board’s built in program; Sharp Touch Viewing software allows us to easily manipulate and edit our documents (jpegs and PDFs) all at the same time on the dashboard.

George Khoury

Sharp PN-40TC1 Huddle Board

The biggest perks for me would be that it comes with easy to use and comprehensive programs that make the collaboration process a whole lot more intuitive and organic

David Coyle

Brother PocketJet PJ-773 A4 Portable Thermal Printer

I rate the printer as a 5 out of 5 stars as it has been able to fit seamlessly into my busy and mobile lifestyle.

Kurt Hegetschweiler

Brother PocketJet PJ-773 A4 Portable Thermal Printer

It’s perfect for mobile workers. Just take it out — it’s small enough to sit anywhere — turn it on, load a sheet of paper, and start printing.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?