CVE-2026-109949 Overview
CVE-2026-109949 affects FreeRDP versions 3.0.0 through 3.31.x, where the virtual smartcard Generic Identity Device Specification (GIDS) implementation improperly restricts authentication attempts. The vulnerability stems from storing the PIN retry counter per-handle rather than persistently. A malicious Remote Desktop Protocol (RDP) server can exhaust the counter using VERIFY Application Protocol Data Units (APDUs), then request a new SCardConnect to reset the retry count. This behavior enables unbounded online brute-forcing of the configured smartcard PIN. The weakness is classified under [CWE-307: Improper Restriction of Excessive Authentication Attempts].
Critical Impact
A hostile RDP server can brute-force a client's smartcard PIN during an interactive session, compromising confidentiality of the credential material.
Affected Products
- FreeRDP 3.0.0 through 3.31.x (virtual smartcard GIDS implementation)
- Applications and distributions bundling vulnerable FreeRDP 3.x libraries
- RDP client workflows that use virtual smartcard redirection
Discovery Timeline
- 2026-10-13 - CVE-2026-109949 published to the National Vulnerability Database (NVD)
- 2026-10-13 - Last updated in NVD database
Technical Details for CVE-2026-109949
Vulnerability Analysis
FreeRDP implements a virtual smartcard using the GIDS applet to support redirected smartcard authentication. The GIDS applet tracks failed PIN attempts via a retry counter intended to lock the card after repeated failures. In the vulnerable implementation, this counter lives in per-handle state rather than persistent card state. A malicious RDP server submits repeated VERIFY APDUs to exhaust the counter, then triggers a fresh SCardConnect call. The reconnection yields a new handle with a reinitialized counter, defeating the lockout entirely.
Root Cause
The root cause is improper scoping of authentication state. Retry counters must be bound to the simulated card, not to a transient client-server handle. Because FreeRDP reset the counter on every new context, the lockout protection required by [CWE-307] never triggered under adversarial reconnection patterns.
Attack Vector
Exploitation requires a victim to initiate an RDP connection to an attacker-controlled server with smartcard redirection configured. The attack is network-based and requires user interaction to establish the session. Once the session is live, the server issues VERIFY APDUs to the virtual smartcard, cycling connections to brute-force the PIN. Successful recovery of the PIN exposes the credential needed to authenticate with the physical smartcard.
No verified public proof-of-concept code is available. See the FreeRDP GitHub Security Advisory and VulnCheck Advisory for FreeRDP for the authoritative technical description.
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Stop Identity AttacksDetection Methods for CVE-2026-109949
Indicators of Compromise
- Outbound RDP sessions to untrusted or newly observed servers that negotiate smartcard redirection channels (rdpsnd, rdpdr, SCARD).
- High-frequency SCardConnect and SCardDisconnect cycles originating from a single RDP session.
- Repeated VERIFY APDU traffic (INS=0x20) over the SCARD virtual channel within short time windows.
Detection Strategies
- Inspect FreeRDP client logs for abnormal smartcard reconnection sequences during a single session.
- Baseline normal smartcard PIN entry patterns and alert on volumes exceeding typical card lockout thresholds.
- Monitor host telemetry for FreeRDP client processes connecting to RDP endpoints outside approved jump host inventories.
Monitoring Recommendations
- Centralize RDP client logs in a security data lake and correlate repeated smartcard reconnect events with destination reputation.
- Deploy endpoint detection and response (EDR) rules that flag FreeRDP connections to non-corporate destinations when smartcard redirection is enabled.
- Alert on process command lines invoking FreeRDP (xfreerdp, wlfreerdp) with /smartcard or /sc redirection flags against unapproved hosts.
How to Mitigate CVE-2026-109949
Immediate Actions Required
- Upgrade all FreeRDP 3.x installations to version 3.32.0 or later.
- Audit any downstream software or Linux distribution packages that embed FreeRDP and apply vendor-rebuilt updates.
- Restrict outbound RDP connections to approved servers through firewall policy or jump host enforcement.
Patch Information
The FreeRDP maintainers fixed the issue in release 3.32.0. Details are documented in the FreeRDP GitHub Security Advisory GHSA-chh2-527f-x255. The fix moves the PIN retry counter into persistent virtual card state so that reconnection no longer resets the lockout.
Workarounds
- Disable smartcard redirection in FreeRDP client invocations until the patched version is deployed.
- Connect only to trusted RDP servers under administrative control, and reject connections to unverified hosts.
- Use a strong, high-entropy smartcard PIN to increase the cost of any brute-force attempt during the exposure window.
# Example: launch xfreerdp without smartcard redirection as a temporary workaround
xfreerdp /v:rdp.example.corp /u:alice /cert:tofu
# Note: omit the /smartcard or /sc options until FreeRDP >= 3.32.0 is installed
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
