CVE-2026-109948 in FreeRDP
Summary
by MITRE • 10/13/2026
FreeRDP from 3.0.0 before 3.32.0 contains an uninitialized memory disclosure vulnerability in smartcard_Transmit_Call that allows malicious RDP servers to read client memory. Servers can send SCardTransmit requests with an invalid card handle and nonzero receive length, causing smartcard_pack_transmit_return to serialize up to 66,560 uninitialized heap bytes.
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Analysis
by VulDB Data Team • 10/13/2026
The vulnerability identified in FreeRDP versions prior to 3.32.0 represents a critical information disclosure flaw located within the smart card transmission handling logic. Specifically, the defect resides in the smartcard_Transmit_Call function and its associated serialization routine, smartcard_pack_transmit_return. This issue arises from improper initialization of memory buffers used during the processing of PC/SC protocol commands. When an RDP client receives a SCardTransmit request from a malicious or compromised remote server, it attempts to process the command by allocating heap memory for the response data. The core technical failure occurs when the server provides an invalid card handle alongside a nonzero receive length parameter. In this specific scenario, the application fails to properly initialize the output buffer before attempting to populate it with data derived from the smart card device or simulated environment. Consequently, instead of returning only the valid bytes retrieved from the card, the serialization function proceeds to pack and transmit uninitialized heap memory up to a maximum size of 66,560 bytes back to the client application for inclusion in the response packet sent to the server.
This architectural flaw allows an attacker operating as a malicious RDP server to perform remote information disclosure by reading arbitrary contents from the FreeRDP client process memory space. By carefully crafting SCardTransmit requests with specific invalid handles and length parameters, the attacker can trigger the serialization of sensitive data that was previously allocated on the heap but not yet overwritten or cleared. This exposed memory may contain cryptographic keys, session tokens, authentication credentials, clipboard contents, or other private user data currently held in active use by the application. The impact is severe as it bypasses standard access controls and allows for non-intrusive exfiltration of confidential information without requiring code execution privileges on the client machine. This type of vulnerability aligns with CWE-200, which categorizes exposure of sensitive information to an unauthorized actor, and specifically relates to improper initialization leading to memory leakage.
From a threat intelligence perspective, this exploitation technique maps directly to MITRE ATT&CK tactic T1530, Data from Local System, and more specifically the sub-technique T1530.001, which covers data from cloud storage or local file systems via unauthorized access mechanisms such as memory scraping in this context. The attack vector is remote through the RDP protocol, requiring no user interaction beyond establishing a connection to the malicious server. This makes it particularly dangerous in enterprise environments where users may connect to untrusted or compromised virtual desktop infrastructure hosts.
Mitigation strategies primarily involve upgrading FreeRDP to version 3.32.0 or later, where this initialization defect has been addressed by ensuring that all buffers are zeroed out before use regardless of the validity of the card handle provided in the request. For organizations unable to immediately patch their endpoints, network-level controls such as firewalls and intrusion detection systems can be configured to inspect RDP traffic for anomalous SCardTransmit patterns or unusually large response sizes originating from smart card channels. Additionally, restricting user permissions within FreeRDP sessions and disabling unnecessary smart card redirection features when not explicitly required by business operations can reduce the attack surface available to adversaries attempting to exploit this memory disclosure vector.