CVE-2026-121391

A flaw was found in FreeRDP. When parallel-device redirection is enabled, a malicious Remote Desktop Protocol (RDP) server can cause a Denial of Service (DoS) on a connecting client by sending repeated device open requests. Due to a resource management flaw, the client fails to close previous file descriptors upon receiving subsequent requests. This behavior enables a hostile server to exhaust the client's available file handles, ultimately causing the FreeRDP client process to crash.

This vulnerability is rated as Moderate impact for Red Hat products because exploitation requires a client to initiate an RDP session to an untrusted server while explicitly enabling parallel device redirection, limiting the failure impact strictly to client denial of service. Under standard deployments, parallel port redirection is not enabled by default, requiring specific user configuration to expose the affected functionality. Furthermore, the issue only exhausts client-side file descriptors without allowing code execution or compromising the host system outside of the terminating FreeRDP process.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Disable parallel device redirection when connecting to remote RDP endpoints.

Ensure that client connection configurations or command-line invocations do not enable parallel device redirection (such as omitting the /parallel option). Additionally, restrict connections strictly to trusted and authenticated RDP hosts to prevent untrusted servers from triggering client resource exhaustion.

Caveats: Disabling parallel port redirection prevents remote RDP sessions from interacting with local parallel devices.