Security News > 2021 > December > Microsoft December 2021 Patch Tuesday fixes 6 zero-days, 67 flaws
Today is Microsoft's December 2021 Patch Tuesday, and with it comes fixes for six zero-day vulnerabilities and a total of 67 flaws.
Microsoft has fixed 55 vulnerabilities with today's update, with seven classified as Critical and 60 as Important.
December's Patch Tuesday includes fixes for six zero-day vulnerabilities, with one actively exploited Windows AppX Installer vulnerability.
Microsoft classifies a vulnerability as a zero-day if it is publicly disclosed or actively exploited with no official fix available.
Microsoft also fixed five publicly disclosed zero-day vulnerabilities as part of the December 2021 Patch Tuesday that are not known to be exploited in attacks.
Below is the complete list of resolved vulnerabilities and released advisories in the December 2021 Patch Tuesday updates.
News URL
Related news
- Microsoft April 2025 Patch Tuesday fixes exploited zero-day, 134 flaws (source)
- Patch Tuesday: Microsoft Fixes 134 Vulnerabilities, Including 1 Zero-Day (source)
- Microsoft May 2025 Patch Tuesday fixes 5 exploited zero-days, 72 flaws (source)
- Patch Tuesday: Microsoft fixes 5 actively exploited zero-days (source)
- April 2025 Patch Tuesday forecast: More AI security introduced by Microsoft (source)
- New Windows zero-day leaks NTLM hashes, gets unofficial patch (source)
- Zero-Day Alert: Google Releases Chrome Patch for Exploit Used in Russian Espionage Attacks (source)
- Week in review: Probing activity on Palo Alto Networks GlobalProtect portals, Patch Tuesday forecast (source)
- Microsoft: Windows CLFS zero-day exploited by ransomware gang (source)
- Microsoft fixes actively exploited Windows CLFS zero-day (CVE-2025-29824) (source)