CVE-2026-50523: Microsoft PowerShell Local Command Injection Vulnerability

Overview

CVE-2026-50523 is a high-severity command injection vulnerability in Microsoft PowerShell. The flaw stems from improper neutralization of special elements within command processing, classified under CWE-77 (Improper Neutralization of Special Elements used in a Command). An authorized local attacker can exploit this vulnerability to execute arbitrary code in the context of the PowerShell process.

The vulnerability carries a CVSS base score of 7.8, indicating high severity with local attack vector, low attack complexity, and no privileges or user interaction required beyond having local access.

Technical Details

Command injection vulnerabilities occur when user-supplied input containing shell metacharacters or command delimiters is passed unsanitized to a command interpreter. In the case of PowerShell, the affected code paths fail to properly sanitize or escape input before constructing and executing system commands.

The CWE-77 classification (Command Injection) is distinct from OS command injection (CWE-78) in that the injected commands are interpreted by the application's own command parser rather than directly by the underlying operating system shell. In PowerShell, this distinction can blur given PowerShell's deep integration with the Windows scripting environment and its ability to invoke .NET methods, COM objects, and external executables.

Typical exploitation patterns include:

# Vulnerable pattern — unsanitized user input passed to Invoke-Expression or similar
$userInput = "; Get-Process | Stop-Process -Force"
Invoke-Expression "Get-Item $userInput"
 
# Or via Start-Process / & operator with injectable strings
& $userControlledPath

Because PowerShell is deeply embedded in Windows administration workflows, scripts and automation tools that accept external input without validation are particularly exposed.

Affected Components

• Product: Microsoft PowerShell
• Attack Vector: Local
• Attack Complexity: Low
• Privileges Required: Low (authorized local attacker)
• User Interaction: None
• Scope: Unchanged
• Confidentiality / Integrity / Availability: High / High / High

Impact

Successful exploitation by a locally authorized attacker can result in:

• Arbitrary code execution within the PowerShell process security context
• Privilege escalation if PowerShell is running with elevated permissions
• Data exfiltration through PowerShell's built-in networking cmdlets
• Persistence mechanisms via registry manipulation, scheduled tasks, or startup scripts
• Lateral movement through PowerShell remoting if WinRM is enabled

Given PowerShell's privileged role in Windows environments and its frequent use in DevOps pipelines, CI/CD tooling, and IT automation scripts, the blast radius of exploitation can extend well beyond a single workstation.

Mitigation

1. Apply Microsoft patches: This vulnerability was disclosed as part of Microsoft's August 2026 Patch Tuesday. Install the relevant cumulative updates for your Windows and PowerShell versions immediately.
2. Constrained Language Mode: Enable PowerShell Constrained Language Mode (CLM) for non-administrative users and automated scripts that do not require full language capabilities.
3. Script Block Logging: Enable PowerShell script block logging (HKLM:\SOFTWARE\Policies\Microsoft\Windows\PowerShell\ScriptBlockLogging) to capture injected commands for forensic analysis.
4. Input validation in scripts: All PowerShell scripts accepting external input should validate and sanitize parameters. Avoid Invoke-Expression with user-controlled data. Use -LiteralPath over -Path where applicable.
5. Least privilege: Run automation scripts with the minimum required permissions. Avoid running PowerShell scripts as SYSTEM or Domain Admin without necessity.
6. AMSI integration: Ensure Windows Antimalware Scan Interface (AMSI) is enabled and your endpoint protection solution has an AMSI provider registered — it inspects PowerShell script content before execution.

References

• NVD — CVE-2026-50523
• Microsoft Security Update Guide
• CWE-77: Improper Neutralization of Special Elements used in a Command