CVE-2026-67303
Received Received - Intake

Denial of Service in FreeRDP via Serial Device Redirection

Publication date: 2026-08-01

Last updated on: 2026-08-01

Assigner: VulnCheck

Description
FreeRDP before 3.29.0 contains a reachable assertion (WINPR_ASSERT(OutputBufferLength == BytesReturned)) in serial_process_irp_device_control() in channels/serial/client/serial_main.c. When serial device redirection is enabled and a server-controlled IRP_MJ_DEVICE_CONTROL request specifies an unsupported IOCTL with a non-zero OutputBufferLength, CommDeviceIoControl() can fail with BytesReturned = 0, causing the mismatch to trigger the assertion and abort the client process (denial of service).

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Meta Information

Published
2026-08-01
Last Modified
2026-08-01
Generated
2026-08-01
AI Q&A
2026-08-01
EPSS Evaluated
N/A
NVD
CVE-2026-67303
EUVD
EUVD-2026-51818

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
freerdp freerdp to 3.29.0 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-617 The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.

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Executive Summary

FreeRDP before version 3.29.0 has a flaw in its serial device redirection feature. When enabled, a server can send a malicious request with an unsupported command and a non-zero output buffer size. This causes the client to fail with a zero-byte response, triggering an internal assertion error that crashes the FreeRDP client process, leading to a denial of service.

Detection Guidance

Detecting this vulnerability requires checking FreeRDP versions and monitoring for crashes during serial device redirection. Use 'freerdp --version' to verify if your version is below 3.29.0. Monitor system logs for assertion failures in serial_main.c during serial device redirection attempts.

Impact Analysis

If you use FreeRDP with serial device redirection enabled and connect to a malicious or compromised server, the client may crash unexpectedly. This disrupts remote desktop sessions and could lead to loss of access to the remote system until the client is restarted.

Mitigation Strategies

Upgrade FreeRDP to version 3.29.0 or later. Disable serial device redirection if not required. Apply patches if available from your distribution. Monitor for crashes or denial of service conditions related to serial device control.

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