Windows - Security - Mitigate CVE-2023-38149

What the CVE-2023-38149 mitigation Worklet does

This Automox Worklet™ protects Windows endpoints from CVE-2023-38149, a denial of service vulnerability in the Windows TCP/IP stack. The Worklet implements Microsoft's recommended mitigation by disabling router discovery on all IPv6 network interfaces.

Router discovery allows IPv6 interfaces to automatically learn about routers on the network. Disabling this feature prevents attackers from exploiting the vulnerability through malicious router advertisement packets.

This Worklet serves as a stopgap measure. Microsoft strongly recommends installing the official security updates as soon as they become available, even if you keep this mitigation in place. Use the revert parameter to restore router discovery after applying patches.

Why disable IPv6 router discovery

Remote attackers can cause a denial of service condition on vulnerable Windows systems through specially crafted network packets targeting the IPv6 router discovery mechanism. CVE-2023-38149 allows remote attackers to exploit this vulnerability, potentially disrupting endpoint availability.

Disabling router discovery prevents the vulnerable code path from processing malicious packets. This mitigation may affect IPv6 connectivity in environments that rely on router advertisements for address configuration, so test before broad deployment.

Organizations that cannot immediately deploy security updates benefit from this interim protection. The Worklet provides documented, reversible changes that reduce attack surface while you schedule maintenance windows for patching.

How IPv6 router discovery mitigation works

1. Evaluation phase: The Worklet retrieves all IPv6 interfaces using Get-NetIPInterface and checks the RouterDiscovery property on each. If any interface has router discovery enabled, the endpoint requires remediation. If the revert parameter is set and router discovery is already disabled, it also triggers remediation to restore settings.

2. Remediation phase: The Worklet iterates through all IPv6 interfaces and applies Set-NetIPInterface with RouterDiscovery set to Disabled (or Enabled if reverting). Each interface modification is logged with its alias and index number for troubleshooting.

CVE-2023-38149 mitigation requirements

• Windows workstations or servers with IPv6 enabled

• Administrative privileges to modify network interface settings

• No restart required after applying changes

• Parameter: Revert (set to true to restore router discovery)

• Test IPv6 connectivity impact in your environment before deployment

Expected IPv6 network configuration state

After successful remediation, all IPv6 interfaces have router discovery disabled. You can verify by running Get-NetIPInterface -AddressFamily IPv6 in PowerShell and checking the RouterDiscovery column shows Disabled for all entries. This configuration protects your endpoints from CVE-2023-38149 exploitation until Microsoft patches can be deployed.

Subsequent Worklet executions confirm the endpoint maintains the mitigation. After applying Microsoft's security updates, run the Worklet with the revert parameter to restore router discovery functionality. Monitor your environment for any IPv6 connectivity issues after applying this mitigation, as some environments may require router advertisements for proper address configuration.

How to validate mitigate cve-2023-38149 changes

1. Run this Worklet on a pilot Windows endpoint and review evaluation output for mitigate cve-2023-38149.

2. Confirm Automox activity logs show successful completion and exit code 0.

3. Verify endpoint state using checks aligned to evaluation script logic, such as Get-NetIPInterface, Write-Verbose.

4. Validate remediation effects from script operations such as Get-NetIPInterface, Set-NetIPInterface, Write-Verbose, then rerun evaluation for compliance.

For technical validation, compare endpoint state to the Worklet evaluation logic and remediation flow for mitigate cve-2023-38149. This supports repeatable security workflows, faster change control review, and auditable compliance evidence.

Useful script references for this Worklet include evaluation operations such as Get-NetIPInterface, Write-Verbose and remediation operations such as Get-NetIPInterface, Set-NetIPInterface, Write-Verbose. Use these indicators to verify that endpoint changes match intended policy outcomes.