CVE-2026-91947 FreeRDP CVE debrief

Who should care

Defenders responsible for FreeRDP servers, especially those exposed to untrusted or authenticated clients, should assess their exposure and prioritize patching or mitigating this vulnerability.

Why it matters

CVE-2026-91947 is a high-severity use-after-free vulnerability in FreeRDP server versions before 3.31.0. Defenders should prioritize patching or mitigating this vulnerability, especially in environments where FreeRDP servers are exposed to untrusted or authenticated clients.

• Potential remote code execution or denial of service
• Requires authentication and specific conditions to be triggered
• Patching or mitigating this vulnerability is crucial to prevent exploitation

Technical summary

The vulnerability exists in the DRDYNVC parser of FreeRDP server versions before 3.31.0. An authenticated client can trigger a use-after-free condition by racing AUDIN channel closure messages against DRDYNVC data parsing, potentially leading to heap-use-after-free when accessing freed channel objects. This requires authentication and specific conditions to be triggered. Defenders should prioritize patching or mitigating this vulnerability, especially in environments where FreeRDP servers are exposed to untrusted or authenticated clients. The vulnerability can lead to potential remote code execution or denial of service.

Defensive priority

Defenders should prioritize patching or mitigating this vulnerability, especially in environments where FreeRDP servers are exposed to untrusted or authenticated clients.

Recommended defensive actions

• Patch FreeRDP servers to version 3.31.0 or later
• Restrict access to FreeRDP servers to trusted clients only
• Monitor FreeRDP server logs for suspicious 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 described in the CVE record and NVD entry. FreeRDP server versions before 3.31.0 are affected. The vulnerability requires authentication and specific conditions to be triggered. Evidence is limited to CVE and NVD details. Defenders should verify FreeRDP server versions and configurations, review AUDIN and DRDYNVC channel interactions, and monitor for suspicious activity.

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.