CVE-2026-109949 in FreeRDP
Summary
by MITRE • 10/13/2026
FreeRDP 3.0.0 before 3.32.0 contains an improper restriction of excessive authentication attempts in its virtual smartcard GIDS implementation, which stores the PIN retry counter per-handle. A malicious RDP server can exhaust the counter with VERIFY APDUs, then request a new SCardConnect to reset attempts, enabling unbounded online brute-forcing of the configured smartcard PIN.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/13/2026
The vulnerability identified in FreeRDP versions prior to 3.32.0 represents a critical flaw within its implementation of virtual smart card functionality, specifically affecting the Global Identity Service (GIDS) component. This issue stems from an improper restriction of excessive authentication attempts, which fundamentally undermines the security mechanisms designed to protect sensitive credentials stored on hardware or emulated smart cards. The core technical deficiency lies in how the application manages state for PIN retry counters during the connection lifecycle. Specifically, FreeRDP stores these counters on a per-handle basis rather than maintaining them across distinct session connections that utilize the same underlying credential material. This architectural decision creates a significant gap in security enforcement, allowing attackers to bypass standard rate-limiting protections that are typically intended to prevent brute-force attacks against authentication tokens.
From an operational perspective, this flaw enables a malicious Remote Desktop Protocol (RDP) server to execute unbounded online brute-forcing of the configured smart card PIN. The attack vector relies on the interaction between the client and the compromised or rogue RDP server. An attacker controlling the remote end can send VERIFY APDU commands designed to deliberately fail authentication, thereby incrementing the retry counter associated with the current connection handle. Once the system detects that the maximum number of allowed attempts has been reached for that specific session, it typically locks out further attempts to protect the credential. However, because FreeRDP resets this state when a new SCardConnect request is initiated, an attacker can simply establish a fresh connection and repeat the process indefinitely. This effectively neutralizes any protective measures intended to limit guessing attacks, allowing the adversary to systematically test every possible PIN combination without fear of account lockout or temporary suspension.
The impact of this vulnerability extends beyond simple credential compromise; it facilitates unauthorized access to systems protected by smart card authentication, which is often deployed in high-security environments requiring multi-factor verification. By bypassing these controls through automated brute-forcing, an attacker can gain full administrative privileges if the compromised credentials belong to a privileged user account. This undermines the integrity of zero-trust architectures and identity-based security models that rely on hardware tokens as a primary factor for access control. The ability to exhaustively search PIN space without restriction significantly reduces the time required to compromise weak or predictable passcodes, rendering even complex smart card solutions vulnerable if users select easily guessable personal identification numbers.
This vulnerability aligns with CWE-307, which describes Improper Restriction of Excessive Authentication Attempts, as it fails to enforce adequate limits on repeated login attempts across related sessions. Furthermore, the exploitation technique maps directly to MITRE ATT&CK T1110.004, representing Brute Force: Password Guessing for Smart Cards and Tokens. The attack leverages standard smart card communication protocols (APDUs) to manipulate state in a way that circumvents intended security controls, highlighting a failure in both input validation and session management logic within the virtualization layer of the RDP client.
Mitigation strategies must focus on immediate software updates and architectural reviews. Organizations running FreeRDP should upgrade to version 3.32.0 or later, where this state management issue has been addressed by ensuring that PIN retry counters are persisted across connection resets for the same smart card instance. Until an update is applied, administrators can implement network-level controls such as firewalls and intrusion detection systems to monitor for anomalous patterns of RDP connections originating from single sources, which may indicate brute-force activity. Additionally, enforcing strong PIN policies through group policy or local security settings can reduce the attack surface by eliminating predictable passcodes that are susceptible to rapid guessing. It is also advisable to review smart card usage policies and consider implementing additional layers of authentication where possible to ensure that no single factor remains a sole point of failure against automated attacks.