New vulnerability discovered in Cisco ASA, ASAx and Firepower devices

New vulnerability discovered in Cisco ASA, ASAx and Firepower devices

A new vulnerability was publicly announced last Friday (22th of June). It effects all current Cisco ASA devices (all models) and Firepower appliances (please see full list below).

It allows a remote attacker to execute a DoS (Denial-Of-Service) attack towards the vulnerable device and potentially extract sensitive data from the device (credential usernames and active sessions). It exploits the HTTP(S) service on the devices and uses directory traversal to try to gather sensitive data and potential reload the device. The vulnerability is possible due to lack of proper input validation of the HTTP URLs.

The discovery was made by a Polish Security researcher named Michal Bentkowski and was initially shared only with Cisco, giving time for Cisco to prepare patches and updates to its software. There have already been real-life attempts in exploiting this vulnerability due its lack of complexity and how easy it is to do it – there is already a couple of scripts on the internet to automate the process (see links below). Cisco states there is no work-around for this problem and all its customers are urged to upgrade to the patched software that Cisco has released prior to the unveiling of the vulnerability.

How to check if your devices are vulnerable:

If you have not patched your devices since the 22th of June and are using ASDM/CSM or Anyconnect on a publicly facing interface then it is very likely you are affected.

Simple steps to validate if your devices are vulnerable

1. Check if your devices is listening on SSL ports

 ciscoasa# show asp table socket | include SSL|DTLS

Look for open sockets on public facing interfaces

2. Check for presence of a process called Unicorn Proxy Thread, if this process is present, your device is considered vulnerable

ciscoasa# show processes | include Unicorn
Mwe 0x0000557f9f5bafc0 0x00007f62de5a90a8 0x0000557fa52b50a0
 3632 0x00007f62c8c87030 30704/32768 Unicorn Proxy Thread 218

Look for open sockets on public facing interfaces

Affected models:

  • 3000 Series Industrial Security Appliance (ISA)
  • ASA 1000V Cloud Firewall
  • 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
  • Adaptive Security Virtual Appliance (ASAv)
  • Firepower 2100 and 4100 Series Security Appliance
  • Firepower 9300 ASA Security Module
  • FTD Virtual (FTDv)

Fixed Releases:

Customers should upgrade to an appropriate release as indicated in the following tables.

Cisco ASA Software

Cisco ASA Software ReleaseFirst Fixed Release for This Vulnerability
Prior to 9.11Migrate to
9.3 Migrate to
9.5Migrate to

Cisco FTD Software

Cisco FTD Software ReleaseFirst Fixed Release for This Vulnerability
6.0Migrate to 6.1.0 HotFix or later
6.0.1Migrate to 6.1.0 HotFix or later (all FTD hardware platforms except 41xx and 9300) (41xx and 9300 FTD hardware platforms)
6.2.0Not vulnerable
6.2.1Migrate to

Cisco Security

End of the Traditional Firewalls Era – Cisco ASA is not enough anymore

Cisco Security


Malware has evolved so much in recent years and the trend is to keep evolving with ever increasing pace. Traditional Firewalls that use old technologies such as stateful firewalling are not capable of detecting / preventing most of the modern threats. The restricted use of traditional firewalls to lower the attack surface is not sufficient and not effective anymore. Vulnerabilities get discovered every day, many of them critical, server administrators often lack the required knowledge to protect/patch their devices. Endpoints (desktops/laptops/smartphones) are constantly at risk due to the fact bad “actors” are constantly coming up with clever ways to bypass traditional defenses and deliver malware, quite often exploiting the weakest link (the users), companies cannot cope with training users in the field of IT security quick enough.

Before, now and future

It is obvious that additional security on the network layer is mandatory. But the controls that are to be used must meet certain criteria, they must be what the industry call Next-Generation Firewall, meaning the device should be able to identify users, applications, do advanced threat protection using different methods (signatures, reputation, sandboxing) and provide detailed reports/logs for pro-active and reactive (forensics) purposes. All current high-end vendors on the market provide this Next-Gen FW capability. Cisco has done something very clever, it decided many years ago (after the purchase of Sourcefire) that it would integrate the Sourcefire functionality into its Firewall technology and is dominating the market with its next generation ASA products. The result was a very flexible solution, albeit a bit cumbersome to configure. The client has the option to enable just the ASA functionality and hence have only a stateful Firewall, or also add the advanced Sourcefire Next-Gen FW capabilities. Cisco even sells all current devices (the 5500 X series) with a built in Firepower (Cisco rebranded Sourcefire into Firepower) capability. A significant number of customers are actively replacing the older ASAs with new X series ones. Many without enabling the Firepower capability. As mentioned briefly above, the reasons for this decision vary but the main one was the added complexity and the separate management that the Firepower needed. This translates into added cost, as usually these skills are not available internally and had to be sourced from outside consulting companies. Also, the Firepower product cannot just be configured and forgotten about but needs small adjustments and manual intervention from time to time, again adding to the operational costs.

With more customers adopting and embracing the Firepower solution, the solution has matured, especially after the introduction of Firepower 6.1. Installation, integration and support have become more user friendly. Which meant operational costs have reduced significantly. Transition between pure ASA and ASA + Firepower was streamlined and could be done within days and without any downtime for the customer. A small investment in purchasing the licenses for Firepower, as customers already had the hardware, and the additional consulting services could in fact be the difference between a secure network and a compromised one. We all know that this is a very bad and expensive experience. This investment made would immediately start to pay off and ensure a completely different way of securing your network that cannot be compared to the archaic traditional firewalls. In the future Cisco and many other vendors will completely get remove stateful only Firewall devices. Cisco is going to replace all ASA with the new appliances capable of running a united operating system – the Firepower Threat Defense. The switch to this is inevitable, so there are no benefits whatsoever for waiting. The work for the transition/migration must be done and the sooner the better. Simply put, there is more protection and security provided to all resources behind the Firewall.


We urge to our customers not to wait until it is too late. Don’t be reactive to a compromised network, take the initiative today and avoid the inevitable.

If you already have the ASA X series deployed there are just a few simple steps to attain all the benefits from the most advanced Intrusion Prevention system at the moment.

Why wait? Contact 4CornerNetworks today to discuss.