Microsoft February 2026: Six Exploited Zero-Day Vulnerabilities
Microsoft’s February 2026 Patch Tuesday update is not routine. The company patched 59+ vulnerabilities across Windows, Office, and core components — and six of them were already being actively exploited in the wild.
When zero-days are exploited before patches are widely deployed, defenders are no longer preventing attacks — they are responding to ongoing ones.
Security teams worldwide are now racing to close gaps before attackers scale exploitation.
Why This Month Is Different
Six actively exploited zero-days in a single release is unusually high. It indicates coordinated vulnerability discovery and weaponization efforts by threat actors.
Three of the vulnerabilities were publicly disclosed before patching, meaning technical details were already circulating — increasing the probability of rapid exploit development.
Active exploitation means:
- Attack code likely already exists in the wild.
- Threat actors may have operational playbooks built around these flaws.
- Unpatched systems are not theoretical risks — they are active targets.
This is no longer about patch hygiene. It’s about interrupting live attack chains.
The “Big Six” Zero-Days — Analyst Breakdown
🔹 CVE-2026-21510 — Windows Shell Security Feature Bypass
Impact: Bypasses Windows SmartScreen and Mark-of-the-Web (MOTW) protections.
This vulnerability allows attackers to craft shortcut (.lnk) files or shell-executed objects that avoid triggering SmartScreen warnings. Normally, when a file downloaded from the internet carries MOTW metadata, Windows warns the user before execution. This flaw interferes with that trust validation layer.
Why this matters technically: SmartScreen acts as a behavioral “bouncer” between user interaction and code execution. If that gate is bypassed, the system treats untrusted content as locally trusted — dramatically lowering friction for malware delivery.
Example: A phishing email delivers a compressed file containing a malicious shortcut. Due to this flaw, Windows fails to display its normal reputation warning. The user double-clicks, and a PowerShell command executes silently in the background.
🔹 CVE-2026-21513 — MSHTML Framework Security Bypass
Impact: Circumvents embedded browser security checks.
MSHTML (Trident engine) is still used in legacy components and embedded rendering scenarios within Windows and Office. This flaw allows crafted HTML content to bypass execution safeguards, potentially enabling script execution in contexts assumed to be restricted.
Technical concern: Attackers increasingly use HTML-based loaders because they blend into legitimate workflows. A bypass in MSHTML reduces sandbox friction and increases initial access success rates.
Example: A malicious invoice link opens a locally rendered HTML page. The crafted content manipulates MSHTML behavior to execute obfuscated JavaScript that drops a secondary payload.
🔹 CVE-2026-21514 — Microsoft Word Security Feature Bypass
Impact: Weakens Protected View and document trust boundaries.
Microsoft Word typically isolates internet-originated documents in Protected View. This vulnerability interferes with those protections, potentially allowing embedded content or template-based code execution without standard warnings.
Analyst view: Office remains one of the most reliable initial access vectors. Any reduction in its warning system reliability significantly improves phishing campaign effectiveness.
Example: A spoofed vendor email includes a Word document referencing a remote template. Due to the bypass, Word processes embedded components without properly enforcing Protected View restrictions.
🔹 CVE-2026-21519 — Desktop Window Manager (DWM) Privilege Escalation
Impact: Elevation to SYSTEM privileges.
Desktop Window Manager manages graphical rendering and session interactions. A flaw here allows a local attacker to elevate privileges once code execution has been achieved.
Why escalation matters: Initial access is only step one. SYSTEM privileges allow disabling security tools, dumping credentials, and modifying system-level services.
Example: After exploiting CVE-2026-21510 for initial execution, malware leverages this DWM flaw to move from user-level access to full SYSTEM control.
🔹 CVE-2026-21533 — Remote Desktop Services Privilege Escalation
Impact: Local privilege escalation via RDP components.
In enterprise environments where RDP is widely used, this flaw can assist attackers in pivoting after initial compromise.
Example: An attacker with limited user access exploits this vulnerability to escalate privileges and laterally move toward higher-value systems.
🔹 CVE-2026-21525 — Remote Access Connection Manager Denial of Service
Impact: Service disruption affecting remote connectivity.
While not a direct compromise vector, denial-of-service flaws can be used strategically — especially in ransomware campaigns — to destabilize environments or distract defenders during intrusion activity.
The Attack Chain Reality
Individually, these vulnerabilities are dangerous.
Combined, they form a realistic attack chain:
- Phishing Delivery → Malicious shortcut, HTML file, or document.
- Security Feature Bypass → SmartScreen or Protected View suppressed.
- Code Execution → Payload runs without meaningful friction.
- Privilege Escalation → SYSTEM-level access achieved.
- Persistence & Lateral Movement → Enterprise compromise.
This is how modern intrusion operations work — chaining moderate flaws into critical outcomes.
Defensive Priorities
1️⃣ Immediate Patching
Deploy February 2026 cumulative updates across all endpoints and servers. Prioritize internet-facing systems and user workstations.
2️⃣ Validate Enforcement
Ensure SmartScreen, MOTW handling, and Office Protected View operate correctly after patching. Test sample downloads in controlled environments.
3️⃣ Monitor Indicators
- Unusual .lnk execution events
- Unexpected PowerShell or cmd child processes
- Privilege escalation logs (Event ID 4672)
- Abnormal MSHTML-related process activity
4️⃣ Reduce User Click Risk
User interaction remains the ignition point. Reinforce phishing awareness while patches propagate.
ZyberWalls Analyst Take
This Patch Tuesday is a reminder that attackers do not rely on a single breakthrough exploit. They exploit trust boundaries — SmartScreen, Protected View, privilege layers — and look for cracks in the human-to-system interaction model.
The most dangerous vulnerabilities are not always remote code execution bugs. Sometimes they are the ones that quietly remove warnings.
When security friction disappears, human behavior becomes the vulnerability.
Stay Alert. Stay Human. Stay Safe. — ZyberWalls Research Team
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