Threat Response: UPDATE: Vulnerability in Microsoft CryptoAPI (CVE-2020-0601)


Last Tuesday, 14 January, we have informed you about a new vulnerability in Windows related to validation of (Elliptic Curve) certificates [1]. In the meantime, multiple sources have stated that they have found a successful way of exploiting the vulnerability [4][5].

In the earlier message, we discussed two main attack vectors:

  1. Setting up a webpage with an invalid certificate, that is marked as valid by Windows. This tricks the user into thinking they are secure due to, for example, a green padlock being present.
  2. Signing a malicious executable that is marked as valid by Windows, and is then executed without any warnings.

For both ways, a proof of concept has been published. We think there is a high probability that attackers will be able to set up an attack based on the information provided in the publicly available sources.

A way for testing whether an unsafe webpage is being opened without warnings, has been provided by the Internet Storm Center (ISC)[5]. Note: a firewall may block the traffic itself. This test is therefore not 100% reliable.

We have added a detection rule to our Northwave Detection Platform that checks for possible invalid certificates that try to exploit the vulnerability, inside network traffic. This measure does not prevent an attack from being successful. Therefore, we again strongly recommend to install the updates provided by Microsoft [3] as soon as possible, to mitigate a successful attack.

If new critical information about this threat arises we will reach out to you. If you need additional information you can call us by phone or send us an email.

E-mail: [email protected]
Do you have an incident right now? Call our CERT number: +31 (0)85-0437 909 or 0800-1744 (alleen vanuit Nederland)

See the original post of Januari 14th 2020:


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