Responding to KRACK: What You Need To Know

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A new weakness in WPA2 protocol could allow an attacker to read information that was previously assumed to be encrypted, provided the attacker is within the range of the victim.

The weakness was discovered by researchers Mathy Vanhoef and Frank Piessens, from the University of Leuven and has been dubbed KRACK (Key Reinstallation Attack).

Which devices are affected by KRACK?

The KRACK weakness works against all modern, protected Wi-Fi networks. Therefore, if a device supports Wi-Fi, it is most likely affected.

What’s the impact?

The weakness could allow an attacker to decrypt network traffic allowing him/her to steal sensitive information such as credit card numbers, passwords, emails etc. In certain configurations, it could also allow an attacker to inject or forge packets, which could be leveraged to potentially inject malware.

How does it work?

The KRACK weakness affects the Wi-Fi standard itself. This means, the attack works against personal and enterprise Wi-Fi networks as well as older WPA and the latest WPA2 standard, even if the networks only use AES algorithm for encryption.

The vulnerability works by attacking the 4-way handshake of the WPA2 protocol and, in the process, tricking a victim into re-installing a key that’s already in use. Ideally, it should not be possible to reuse a key, but since the WPA2 protocol does not guarantee key reuse, attackers can exploit this weakness by manipulating cryptographic handshakes.

In a typical 4-way handshake, a client will install the key after receiving message 3 of the 4-way handshake. This key is subsequently used to encrypt normal data frames using an encryption protocol. But since messages often get lost/dropped, an access point could resend message 3 multiple times to the client if appropriate acknowledgment was not received. In which case, the client will reinstall the key, and reset the nonces.

If an attacker can reset these nonces at will (which is possible due to this weakness) by collecting and replaying retransmissions of message 3 of the 4-way handshake, the encryption protocol can be attacked resulting in decryption of packets.

Tenable coverage of KRACK

Tenable has released several Nessus® plugins to detect systems affected by the KRACK weakness. The following table summarizes Tenable’s coverage.

Vendor Plugin ID Description
Microsoft 103745 Windows 10 Version 1703 October 2017 Cumulative Update (KRACK)
Microsoft 103746 Windows 7 and Windows Server 2008 R2 October 2017 Cumulative Update (KRACK)
Microsoft 103747 Windows 10 Version 1511 October 2017 Cumulative Update (KRACK)


103748 Windows Server 2012 October 2017 Cumulative Update (KRACK)
Microsoft 103749 Windows 10 Version 1607 and Windows Server 2016 October 2017 Cumulative Update (KRACK)
Microsoft 103750 Windows 8.1 and Windows Server 2012 R2 October 2017 Cumulative Update (KRACK)
Microsoft 103816 Windows 2008 October 2017 Multiple Security Updates (KRACK)
Cisco 103856 Cisco ASA FirePOWER Services Multiple Vulnerabilities in Wi-Fi Protected Access and Wi-Fi Protected Access II (KRACK)
Aruba 103855 ArubaOS WPA2 Key Reinstallation Vulnerabilities (KRACK)
Mikrotik 103857 MikroTik RouterOS < 6.39.3 / 6.40.4 / 6.41rc (KRACK)
FreeBSD 103862 FreeBSD : WPA packet number reuse with replayed messages and key reinstallation (d670a953-b2a1-11e7-a633-009c02a2ab30) (KRACK)
Ubuntu 103863 Ubuntu 14.04 LTS / 16.04 LTS / 17.04 : wpa vulnerabilities (USN-3455-1) (KRACK)
Debian 103859 Debian DSA-3999-1 : wpa – security update (KRACK)
Intel 103870 Intel Wireless Driver Wi-Fi Protected Access II (WPA2) Multiple Vulnerabilities (KRACK)
Fortinet 103873 FortiGate
Ubiquiti Networks 103875 Ubiquiti Networks UniFi (KRACK)

Protecting your organization from KRACK

As patches become available, you should consider which systems expose the network to the greatest risk (those that use Wi-Fi), define a series of checks and then test patches before rolling them to all systems in the network.

Tenable products can assist in identifying systems in the network that may require patching and ensure that systems for which patches are available are properly updated.Tenable will continue to provide coverage for products as patches are rolled out by vendors.

KRACK Dashboard

SecurityCenter® has a new dashboard, WPA2 Key Reinstallation Attack (KRACK) Vulnerability Detection, that focuses specifically on this new weakness. This dashboard provides an analysis of the Wi-Fi infrastructure and the systems that need to be secured against the KRACK vulnerability.

KRACK Dashboard

Stay tuned for more updates

Tenable is keeping a close eye on this story as it develops. Our team will release coverage as additional patches from vendors become available and this post will be updated as new plugins are released.

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About Tenable
Tenable™, Inc. is the Cyber Exposure company. Over 24,000 organizations of all sizes around the globe rely on Tenable to manage and measure their modern attack surface to accurately understand and reduce cyber risk. As the creator of Nessus®, Tenable built its platform from the ground up to deeply understand assets, networks and vulnerabilities, extending this knowledge and expertise into™ to deliver the world’s first platform to provide live visibility into any asset on any computing platform. Tenable customers include over 50 percent of the Fortune 500, large government agencies and organizations across the private and public sectors. Learn more at
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