On January 14, 2020, Microsoft released software fixes to address 49 vulnerabilities as part of their monthly Patch Tuesday announcement. Among the vulnerabilities patched were critical weaknesses in Windows CryptoAPI, Windows Remote Desktop Gateway (RD Gateway), and Windows Remote Desktop Client. An attacker could remotely exploit these vulnerabilities to decrypt, modify, or inject data on user connections:
The updates fixes a serious flaw in the core cryptographic component of widely used Windows 10, Server 2016 and 2019 editions that was discovered and reported to the company by the National Security Agency (NSA) of the United States
The flaw, dubbed 'NSACrypt' and tracked as CVE-2020-0601, resides in the Crypt32.dll module that contains various 'Certificate and Cryptographic Messaging functions' used by the Windows Crypto API for handling encryption and decryption of data.
A cyber attacker could exploit CVE-2020-0601 to obtain sensitive information, such as financial information, or run malware on a targeted system; for example:
- A maliciously crafted certificate could appear to be issued for a hostname that did not authorize it, preventing a browser that relies on Windows CryptoAPI from validating its authenticity and issuing warnings. If the certificate impersonates a user’s bank website, their financial information could be exposed.
- Signed malware can bypass protections (e.g., antivirus) that only run applications with valid signatures. Malicious files, emails, and executables can appear legitimate to unpatched users.
A spoofing vulnerability exists in the way Windows CryptoAPI (Crypt32.dll) validates Elliptic Curve Cryptography (ECC) certificates.
An attacker could exploit the vulnerability by using a spoofed code-signing certificate to sign a malicious executable, making it appear the file was from a trusted, legitimate source. The user would have no way of knowing the file was malicious, because the digital signature would appear to be from a trusted provider.
A successful exploit could also allow the attacker to conduct man-in-the-middle attacks and decrypt confidential information on user connections to the affected software.
The security update addresses the vulnerability by ensuring that Windows CryptoAPI completely validates ECC certificates.
NSA has discovered a critical vulnerability (CVE-2020-0601) affecting Microsoft Windows®1cryptographic 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.
This vulnerability is classed Important and we have not seen it used in active attacks.
Besides Windows CryptoAPI spoofing vulnerability that has been rated 'important' in severity, Microsoft has also patched 48 other vulnerabilities, 8 of which are critical and rest all 40 are important.
It is strongly suggested that you patch this as soon as possible by heading on to your Windows Settings → Update & Security → Windows Update → clicking 'Check for updates on your PC.