CVE-2026-3563: PowerShell Universal DOS Vulnerability

CVE-2026-3563 Overview

CVE-2026-3563 is an improper input validation vulnerability affecting PowerShell Universal's apps and endpoints configuration. This flaw allows an authenticated user with permissions to create or modify Apps or Endpoints to override existing application or system routes. Successful exploitation results in unintended request routing and denial of service via a conflicting URL path.

Critical Impact

Authenticated attackers with app/endpoint creation privileges can disrupt service availability by overriding critical application routes, potentially causing denial of service conditions across the PowerShell Universal deployment.

Affected Products

• Ironmansoftware PowerShell Universal versions prior to 2026.1.4

Discovery Timeline

• 2026-03-17 - CVE-2026-3563 published to NVD
• 2026-03-19 - Last updated in NVD database

Technical Details for CVE-2026-3563

Vulnerability Analysis

This vulnerability stems from insufficient validation of user-supplied input when configuring Apps and Endpoints within PowerShell Universal. The application fails to properly validate URL path configurations, allowing authenticated users to define routes that conflict with existing application or system routes.

When a user with appropriate permissions creates or modifies an App or Endpoint, the system does not adequately check whether the specified URL path collides with pre-existing routes. This oversight enables route hijacking, where legitimate application traffic can be redirected to attacker-controlled endpoints or simply disrupted entirely.

The vulnerability is classified under CWE-1289 (Improper Validation of Unsafe Equivalence in Input), indicating that the application fails to properly recognize when user-supplied route configurations are functionally equivalent to or override existing critical paths.

Root Cause

The root cause is improper input validation in the route configuration logic of PowerShell Universal. Specifically, the application does not enforce uniqueness constraints or priority rules when processing user-defined URL paths for Apps and Endpoints. This allows authenticated users to register paths that shadow or override existing system routes, effectively hijacking request handling for those paths.

Attack Vector

The attack requires network access and authenticated access with elevated privileges (specifically, permissions to create or modify Apps or Endpoints). An attacker meeting these prerequisites can:

1. Authenticate to the PowerShell Universal management interface
2. Create a new App or Endpoint with a URL path that matches an existing system or application route
3. The conflicting route registration overrides the legitimate route
4. Subsequent requests to the affected path are routed to the attacker's endpoint or fail entirely, causing denial of service

The attack primarily impacts the integrity of routing decisions and can cause availability issues for legitimate services. This is a configuration-level attack that exploits insufficient validation in the administrative interface.

Detection Methods for CVE-2026-3563

Indicators of Compromise

• Unexpected changes to App or Endpoint configurations in PowerShell Universal
• New routes that mirror or shadow existing system paths (e.g., /api/v1/, /admin/, /auth/)
• Audit log entries showing route creation by users who don't typically perform these actions
• Service disruptions or routing errors for previously functional application paths

Detection Strategies

• Monitor PowerShell Universal audit logs for route creation and modification events
• Implement alerting on duplicate or overlapping URL path registrations
• Review user activity for accounts with App/Endpoint creation permissions
• Correlate routing errors with recent configuration changes

Monitoring Recommendations

• Enable detailed logging for all administrative actions in PowerShell Universal
• Set up automated alerts for configuration changes to Apps and Endpoints
• Regularly audit route configurations for unexpected or conflicting entries
• Monitor application availability metrics for sudden degradation patterns

How to Mitigate CVE-2026-3563

Immediate Actions Required

• Upgrade PowerShell Universal to version 2026.1.4 or later
• Audit existing Apps and Endpoints configurations for conflicting routes
• Review and restrict permissions for creating or modifying Apps and Endpoints
• Implement change management procedures for route configuration modifications

Patch Information

Ironmansoftware has addressed this vulnerability in PowerShell Universal version 2026.1.4. Organizations should upgrade to this version or later to remediate the vulnerability. For detailed patch information and upgrade instructions, refer to the Devolutions Security Advisory.

Workarounds

• Restrict App and Endpoint creation permissions to only trusted administrators
• Implement a review process for all route configuration changes before deployment
• Maintain an authoritative list of protected system routes and manually verify new configurations against it
• Consider network segmentation to limit exposure of the PowerShell Universal management interface