Improper Authentication in FreeRDP Virtual Smartcard GIDS

Executive Summary

FreeRDP versions 3.0.0 through 3.31.0 have a flaw in their virtual smartcard GIDS implementation. A malicious RDP server can send VERIFY APDUs to exhaust the PIN retry counter, then reset attempts via SCardConnect, allowing unlimited online brute-forcing of the smartcard PIN. The retry counter is stored per-handle and resets upon new connections, bypassing intended lockout mechanisms.

Useful 0 Not Useful 0

Detection Guidance

To detect this vulnerability, check if your FreeRDP version is between 3.0.0 and 3.31.1. Run 'xfreerdp --version' or 'freerdp2 --version' to verify the installed version. If virtual smartcard logon is enabled, monitor RDP server connections for repeated SCardConnect attempts or VERIFY APDU exchanges.

Useful 0 Not Useful 0

Impact Analysis

If you use FreeRDP with virtual smartcard logon enabled, an attacker controlling an RDP server could repeatedly guess your smartcard PIN. A successful guess could allow the attacker to perform protected private-key operations, potentially gaining unauthorized access to systems or data protected by the smartcard.

Useful 0 Not Useful 0

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating confidentiality requirements in GDPR and HIPAA. Organizations using FreeRDP with virtual smartcards may fail compliance audits due to inadequate authentication controls, risking data breaches and regulatory penalties.

Useful 0 Not Useful 0

Mitigation Strategies

Upgrade FreeRDP to version 3.32.0 or later immediately. Disable virtual smartcard logon if not required. If virtual smartcards are necessary, implement account lockout policies and monitor for repeated authentication attempts. Avoid connecting to untrusted RDP servers.

Useful 0 Not Useful 0