Windows 10/Server extreme security flaw

An extremely bad security flaw in Microsoft Windows has just been reported and patched. Here’s more information from the NSA:

NSA has discovered a critical vulnerability (CVE-2020-0601) affecting Microsoft Windows® cryptographic functionality. The certificate validation vulnerability allows an attacker to undermine how Windows verifies cryptographic trust and can enable remote code execution. The vulnerability affects Windows 10 and Windows Server 2016/2019 as well as applications that rely on Windows for trust functionality. Exploitation of the vulnerability allows attackers to defeat trusted network connections and deliver executable code while appearing as legitimately trusted entities. Examples where validation of trust may be impacted include:

o HTTPS connections
o Signed files and emails
o Signed executable code launched as user-mode processes

The vulnerability places Windows endpoints at risk to a broad range of exploitation vectors. NSA assesses the vulnerability to be severe and that sophisticated cyber actors will understand the underlying flaw very quickly and, if exploited, would render the previously mentioned platforms as fundamentally vulnerable. The consequences of not patching the vulnerability are severe and widespread. Remote exploitation tools will likely be made quickly and widely available. Rapid adoption of the patch is the only known mitigation at this time and should be the primary focus for all network owners.

Information from the Department of Homeland Security:

Emergency Directive 20-02
Mitigate Windows Vulnerabilities from January 2020 Patch Tuesday

Information from US-CERT:

Alert (AA20-014A)
Critical Vulnerabilities in Microsoft Windows Operating Systems

Brian Krebs had sounded early alerts:

Cryptic Rumblings Ahead of First 2020 Patch Tuesday

Update, Jan. 14, 9:20 a.m. ET: The NSA’s Neuberger said in a media call this morning that the agency did indeed report this vulnerability to Microsoft, and that this was the first time Microsoft will have credited NSA for reporting a security flaw. Neuberger said NSA researchers discovered the bug in their own research, and that Microsoft’s advisory later today will state that Microsoft has seen no active exploitation of it yet.

According to the NSA, the problem exists in Windows 10 and Windows Server 2016. Asked why the NSA was focusing on this particular vulnerability, Neuberger said the concern was that it “makes trust vulnerable.” The agency declined to say when it discovered the flaw, and that it would wait until Microsoft releases a patch for it later today before discussing further details of the vulnerability.

Update, 1:47 p.m. ET: Microsoft has released updates for this flaw (CVE-2020-0601). Their advisory is here.