Microsoft Windows CryptoAPI Spoofing Vulnerability

Technical Severity

CVSS v3.1 Metrics

HIGH

8.1 / 10

Minimal Risk Critical

Vector Specification

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Exploitation Likelihood

EPSS Prediction

94.09 %

Predictive Probability

Percentile Rank

99.9 th

Documented as more likely to be exploited than 99.9% of known CVEs.

Detection Date

Nov 03, 2021

Remediation Due

May 03, 2022

CISA Catalog Active

Threat Analysis

Microsoft Windows CryptoAPI (Crypt32.dll) contains a spoofing vulnerability in the way it 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. 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 vulnerability is also known under the moniker of CurveBall.

Remediation Directive

Apply updates per vendor instructions.

External Intelligence

CISA

CISA Advisory

https://www.cisa.gov/news-events/directives/ed-20-02-mitigate-windows-vulnerabilities-january-2020-patch-tuesday)