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Microsoft’s February 2026 Patch Tuesday Fixes Active Zero-Day Exploits

Red | Vulnerability Report
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Summary

Microsoft’s February 2026 Patch Tuesday represents a substantial security update addressing 60 vulnerabilities across the Microsoft product ecosystem, including six actively exploited zero-day vulnerabilities that pose immediate threats to enterprise and consumer environments. The security update includes 59 Microsoft vulnerabilities plus one Chromium-based vulnerability affecting Microsoft Edge, spanning severity ratings of 5 Critical, 52 Important, and 2 Moderate. The vulnerabilities encompass 12 Remote Code Execution flaws, 25 Elevation of Privilege vulnerabilities, 6 Information Disclosure issues, 3 Denial of Service weaknesses, 5 Security Feature Bypass vulnerabilities, and 8 Spoofing flaws affecting core Windows components, Microsoft Office applications, Azure cloud services, and development tools.

Of critical concern, six vulnerabilities were confirmed as actively exploited in the wild at the time of patch release, with three having been publicly disclosed prior to Microsoft’s patches becoming available. Additionally, 16 CVEs are assessed as either actively exploited or at increased risk of exploitation, underscoring the urgent need for rapid patch deployment across enterprise environments. The six actively exploited zero-days include CVE-2026-21510 (Windows Shell security feature bypass), CVE-2026-21513 (MSHTML Framework security feature bypass), CVE-2026-21514 (Microsoft Word security feature bypass), CVE-2026-21519 (Desktop Window Manager elevation of privilege), CVE-2026-21525 (Windows Remote Access Connection Manager denial of service), and CVE-2026-21533 (Windows Remote Desktop Services elevation of privilege). All six vulnerabilities have been added to CISA’s Known Exploited Vulnerabilities catalog, indicating confirmed exploitation by threat actors.

The three security feature bypass zero-days (CVE-2026-21510, CVE-2026-21513, CVE-2026-21514) enable attackers to circumvent Windows security controls through social engineering attacks. CVE-2026-21510 allows attackers to bypass Windows SmartScreen and Windows Shell security warnings by convincing users to open malicious links or specially crafted shortcut files. CVE-2026-21513 enables adversaries to circumvent MSHTML Framework protections, achieving code execution when victims open malicious HTML or LNK files. CVE-2026-21514 affects Microsoft Word, bypassing OLE (Object Linking and Embedding) mitigations designed to restrict unsafe COM/OLE control execution, requiring victims to open crafted Office documents. These vulnerabilities are particularly dangerous as they defeat security controls specifically designed to protect users from malicious content, effectively removing critical defensive layers.

The two elevation of privilege zero-days (CVE-2026-21519, CVE-2026-21533) provide local attackers with pathways to escalate privileges to SYSTEM level after gaining initial access to compromised systems. CVE-2026-21519 affects the Desktop Window Manager component responsible for rendering the Windows graphical user interface, while CVE-2026-21533 targets Windows Remote Desktop Services, a critical component for remote system administration. These privilege escalation vulnerabilities are particularly valuable in post-compromise scenarios, enabling attackers who have gained initial foothold access through phishing, social engineering, or other vulnerabilities to escalate to full administrative control, facilitating lateral movement, persistence establishment, and comprehensive network compromise. The sixth zero-day, CVE-2026-21525, represents a denial-of-service vulnerability in Windows Remote Access Connection Manager that can disrupt system availability, notably assessed at moderate severity despite active exploitation.

Beyond the zero-days, this Patch Tuesday addresses critical vulnerabilities in Azure cloud services including CVE-2026-21522 (Azure ACI Confidential Containers command injection enabling privilege escalation) and CVE-2026-23655 (Azure ACI Confidential Containers information disclosure potentially exposing sensitive tokens or cryptographic keys). Microsoft also patched CVE-2026-21511 (Outlook spoofing vulnerability triggered via crafted emails leveraging the preview pane) and multiple remote code execution issues affecting GitHub Copilot integrations within Visual Studio, VS Code, and JetBrains products stemming from prompt injection risks. Additionally, this release introduces phased updates to replace expiring Secure Boot certificates originally issued in 2011, reinforcing platform trust and boot integrity across the Windows ecosystem.

Vulnerability Details

Severity Distribution: 5 Critical, 52 Important, 2 Moderate vulnerabilities
Impact Categories: 12 RCE, 25 EoP, 6 Information Disclosure, 3 DoS, 5 Security Feature Bypass, 8 Spoofing

Six Actively Exploited Zero-Days:

  1. CVE-2026-21510 (Windows Shell) – Bypasses SmartScreen via malicious links/shortcuts
  2. CVE-2026-21513 (MSHTML Framework) – Circumvents MSHTML protections via HTML/LNK files
  3. CVE-2026-21514 (Microsoft Word) – Bypasses OLE mitigations via crafted documents
  4. CVE-2026-21519 (Desktop Window Manager) – Local privilege escalation to SYSTEM
  5. CVE-2026-21533 (Windows Remote Desktop Services) – Local privilege escalation to SYSTEM
  6. CVE-2026-21525 (Windows Remote Access Connection Manager) – Denial of service (moderate severity)

Notable Additional Vulnerabilities:

  • Azure confidential computing flaws (CVE-2026-21522, CVE-2026-23655)
  • Outlook spoofing via preview pane (CVE-2026-21511)
  • GitHub Copilot RCE across development environments
  • Windows Hyper-V remote code execution vulnerabilities
  • Secure Boot certificate replacement initiative

Recommendations

  1. Priority Patching of Six Zero-Days – Immediately deploy patches for CVE-2026-21510, CVE-2026-21513, CVE-2026-21514, CVE-2026-21519, CVE-2026-21525, CVE-2026-21533 (all on CISA KEV)
  2. Comprehensive Service Exposure Review – Identify publicly accessible vulnerable services and patch internet-facing systems first
  3. Implement Network Segmentation – Restrict unauthorized access to limit lateral movement following privilege escalation
  4. Enforce Least Privilege – Minimize user permissions to reduce privilege escalation impact
  5. Accelerated Testing and Deployment – Given volume of EoP flaws and multiple zero-days, prioritize patch deployment for remote access infrastructure and endpoints exposed to user content

MITRE ATT&CK TTPs

Initial Access: T1189, T1566.001, T1566.002 | Execution: T1059, T1203, T1204.001, T1204.002 | Defense Evasion: T1036, T1218, T1553.005 | Privilege Escalation: T1068, T1543.003 | Credential Access: T1552 | Lateral Movement: T1021.001 | Impact: T1499

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