CVE-2026-109248 FreeRDP CVE debrief

Who should care

Defenders responsible for RDP services, especially in environments where RDP is exposed to untrusted networks or users, should assess exposure and prioritize patching or mitigating this vulnerability.

Why it matters

Defenders should prioritize patching or mitigating CVE-2026-109248 due to potential client crashes and DoS via malicious RDP server. Affected versions require verification.

• Potential client crashes when pasting server-copied files
• Possible denial of service (DoS) via malicious RDP server
• Requires verification of affected versions and exposure

Technical summary

The vulnerability exists in the WinPR clipboard function convert_filedescriptors_to_file_list(), which scans a server-controlled FILEDESCRIPTORW cFileName with unbounded _wcschr() and count_special_chars() calls without a NUL-termination guarantee. This allows a malicious RDP server to send an odd-length FILEDESCRIPTORW blob in a CB_FORMAT_DATA_RESPONSE, potentially crashing X11, Wayland, and SDL clients when the user pastes server-copied files. Affected versions require verification. Defenders should assess exposure and prioritize patching or mitigating this vulnerability.

Defensive priority

Defenders should prioritize patching or mitigating this vulnerability, especially in environments where RDP is exposed to untrusted networks or users.

Recommended defensive actions

• Patch FreeRDP to version 3.32.0 or later
• Restrict RDP access to trusted networks and users
• Monitor for suspicious RDP activity
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability is caused by unbounded _wcschr() and count_special_chars() calls without a NUL-termination guarantee in the convert_filedescriptors_to_file_list() function. This function scans a server-controlled FILEDESCRIPTORW cFileName. The vulnerability allows a malicious RDP server to send an odd-length FILEDESCRIPTORW blob in a CB_FORMAT_DATA_RESPONSE. Affected versions require verification. Defenders should verify affected scope, severity, and vendor guidance.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.