Understanding Microsoft’s February 10, 2026 Security Update: What You Need to Know

What Makes a Vulnerability “Critical”?

Not all software bugs are created equal. A vulnerability becomes truly dangerous when it meets one or more of these criteria:

• Allows remote code execution (RCE): Attackers can run malicious code without local access.
• Bypasses security protections: Tricks built-in defenses into letting bad traffic or files run.
• Is easy to exploit at scale: Works with simple techniques like social engineering or widely available tools.
• Affects a widely deployed component: Hit everywhere from servers to laptops.

With that framework in mind, let’s look at the bugs that stand out from Microsoft’s February patch lineup.

Most Critical Vulnerabilities from Feb 10, 2026

1. Windows Shell Security Feature Bypass (CVE-2026-21510)

This flaw lets attackers get around Windows security warnings (such as SmartScreen). That means a malicious file can look benign to both users and the operating system. Because Windows Shell handles how files and shortcuts are launched, this vulnerability is a perfect tool in a social engineering attack, where a user is tricked into opening something seemingly harmless.

Why it matters: Bypassing security controls dramatically lowers the bar for attackers. You don’t need advanced tooling — just a convincing lure.

2. Microsoft Word Security Feature Bypass (CVE-2026-21514)

Documents are still one of the top ways malware spreads. This vulnerability lets crafted Word files bypass internal security checks, making it easier for attackers to deliver payloads via email or shared storage.

Why it matters: Office documents are everywhere in business workflows. A successful exploit can be a stepping stone to deeper compromise.

3. MSHTML Framework Security Bypass (CVE-2026-21513)

MSHTML is the engine used by older Windows components to handle HTML content. Even though it’s been partially superseded by newer browsers, it still exists in many systems and is frequently used indirectly. This flaw can let attackers skip warnings when handling HTML or web-based content.

Why it matters: Legacy components are often overlooked by defenders, but attackers love them because they slip under the radar of many security tools.

4. Remote Code Execution in Notepad (CVE-2026-20841)

Notepad is one of the simplest, most ubiquitous Windows apps. It sounds trivial, but a vulnerability here lets attackers execute code through crafted input. That makes it surprisingly useful in targeted campaigns, especially when paired with social engineering.

Why it matters: Users trust simple utilities and are less likely to question files opened in them.

5. Azure Confidential Containers Elevation of Privilege & Info Disclosure (CVE-2026-21522, CVE-2026-23655)

These vulnerabilities affect Azure’s confidential container technology, which is designed to isolate workloads securely. A privilege escalation or data leak here could undermine that isolation.

Why it matters: Cloud environments are high-value targets, and containment failures can impact multiple tenants or sensitive workloads.

Other Notable Risks

Beyond the biggest headlines, the patch set included a range of elevation of privilege issues in the Windows kernel, networking stacks like HTTP.sys, and even development tools such as GitHub Copilot and Visual Studio. These flaws might not be exploited directly by unsophisticated attackers, but in the wrong hands they can turn a foothold into full control of a system.

What You Should Do Now

Prioritize patching in this order:

• Security bypass and RCE bugs — These are the most likely to be used in widespread attacks.
• Privilege escalation issues — Especially on servers, domain controllers, and exposed services like RDP.
• Cloud and virtualization vulnerabilities — Particularly in multi-tenant or hybrid environments.
• Developer tooling and SDK flaws — These can affect supply chains and build pipelines.

Don’t delay: Many attacks start with a seemingly small or obscure vulnerability, then chain into something far more impactful. Keeping systems updated is one of the most effective defenses available. https://msrc.microsoft.com/update-guide/vulnerability