CVE-2026-109941 FreeRDP CVE debrief

Who should care

Defenders responsible for RDP infrastructure, network administrators, and security teams should be aware of this vulnerability and take steps to mitigate it. This includes reviewing affected product deployments, verifying FreeRDP version and exposure to untrusted networks or users, and updating incident response plans and procedures as necessary. Operators of RDP-based services and applications should also review their systems for potential impact.

Why it matters

CVE-2026-109941 is a high-severity vulnerability in FreeRDP that allows a malicious RD Gateway to cause a client to hang. Defenders should prioritize patching or mitigating this vulnerability, especially in environments where RDP is exposed to untrusted networks or users.

• Potential for denial of service (DoS) attacks against RDP clients
• Possible impact on RDP-based services and applications
• Requires verification of FreeRDP version and exposure to untrusted networks or users
• May require updates to incident response plans and procedures

Technical summary

The vulnerability is caused by an infinite loop in the http_chuncked_read function of FreeRDP. This function is used to read chunked responses from RD Gateways. The vulnerability can be exploited by sending a partial chunk-size line or footer followed by a clean TLS shutdown, causing the client decoder thread to loop forever and freeze. Affected product deployments should be reviewed for exposure to untrusted networks or users, and defenders should prioritize patching or mitigating this vulnerability, especially in environments where RDP is exposed.

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 or upgrade FreeRDP to version 3.32.0 or later
• Implement network-based mitigations, such as blocking or limiting RDP access to trusted networks or users
• Monitor RDP traffic 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 caused by an infinite loop in the http_chuncked_read function of FreeRDP. This function is used to read chunked responses from RD Gateways. The vulnerability can be exploited by sending a partial chunk-size line or footer followed by a clean TLS shutdown, causing the client decoder thread to loop forever and freeze.

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.