+44 1865 950 828 Secure Your Business
Actively exploited

CVE-2020-0601 Microsoft Windows CryptoAPI Spoofing Vulnerability

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.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 3 Nov 2021.
  • Rated High severity (CVSS 8.1, scored by CISA).
  • It has been in the catalogue for 1,829 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

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, aka 'Windows CryptoAPI Spoofing Vulnerability'.

Affected Versions

ProductVersions
Microsoft Windows10 Version 1803 for 32-bit Systems
10 Version 1803 for x64-based Systems
10 Version 1803 for ARM64-based Systems
10 Version 1809 for 32-bit Systems
10 Version 1809 for x64-based Systems
10 Version 1809 for ARM64-based Systems
Microsoft Windows Serverversion 1803 (Core Installation)
2019
2019 (Core installation)
2016
2016 (Core installation)
Microsoft Windows 10 Version 1903 for 32-bit Systemsunspecified
Microsoft Windows 10 Version 1903 for x64-based Systemsunspecified
Microsoft Windows 10 Version 1903 for ARM64-based Systemsunspecified
Microsoft Windows Server, version 1903 (Server Core installation)unspecified

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Microsoft Windows. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing
Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 3 May 2022 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Microsoft Flaws

Get alerts for MicrosoftWe email you when a new Microsoft vulnerability is confirmed as exploited. Add more vendors on Threat Watch.

By signing up you agree to receive Threat Watch alerts. Unsubscribe at any time. See our Privacy Policy.

CVE-2026-96951Microsoft Windows Command Injection VulnerabilityAdded 13 Oct 2026CVE-2026-65660Microsoft SharePoint Code Injection VulnerabilityAdded 25 Sep 2026CVE-2026-81963Microsoft Windows Link Following VulnerabilityAdded 8 Sep 2026CVE-2026-85880Microsoft Windows Heap-Based Buffer Overflow VulnerabilityAdded 8 Sep 2026CVE-2019-1068Microsoft SQL Server Remote Code Execution VulnerabilityAdded 26 Aug 2026CVE-2026-33824Microsoft Internet Key Exchange (IKE) Service Extensions Double Free VulnerabilityAdded 18 Aug 2026

All 390 exploited Microsoft vulnerabilities

Not Sure If You Are Exposed?

Our attack surface and vulnerability teams can check your internet-facing estate for CVE-2020-0601 and every other exploited flaw on the list.

Check My Exposure
Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2020-0601
  3. CVE record: CVE-2020-0601
  4. FIRST EPSS
  5. portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0601
  6. packetstormsecurity.com/files/155961/CurveBall-Microsoft-Windows-CryptoAPI-Spoofing-Proof-Of-Concept
  7. packetstormsecurity.com/files/155960/CurveBall-Microsoft-Windows-CryptoAPI-Spoofing-Proof-Of-Concept