CVE-2026-110836 in FreeRDP
Summary
by MITRE • 10/15/2026
FreeRDP from 3.0.0 before 3.32.0 contains an infinite loop vulnerability in http_response_recv() that allows malicious gateways to exhaust client CPU via crafted Content-Type headers. Attackers controlling a gateway can return a nonzero Content-Length with a semicolon-containing unrecognized Content-Type, pinning a client thread at full CPU indefinitely.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified within FreeRDP versions ranging from 3.0.0 up to but not including 3.32.0 represents a significant denial of service risk stemming from improper input validation and loop control logic in the HTTP response parsing module. Specifically, the flaw resides in the http_response_recv function, which is responsible for processing incoming HTTP responses during Remote Desktop Protocol sessions that traverse an HTTP gateway. The core technical issue involves how the client handles Content-Type headers that contain semicolons followed by unrecognized parameters when a nonzero Content-Length header is also present. Under normal circumstances, FreeRDP expects well-formed MIME type declarations or standard parameter structures. However, the parsing logic fails to correctly terminate its processing loop when encountering these specific malformed sequences, leading to an infinite execution state rather than gracefully rejecting the invalid input or skipping past it.
From a technical perspective, this flaw allows an attacker who controls the intermediary gateway server to craft HTTP responses that trigger this condition indefinitely. By setting a nonzero Content-Length header alongside a Content-Type header containing semicolons and unrecognized values, the malicious gateway forces the FreeRDP client into a tight loop within the http_response_recv function. This loop consumes one full CPU core on the victim's machine without yielding control to other processes or threads. The result is a sustained denial of service condition where the affected system becomes unresponsive due to resource exhaustion, effectively rendering the remote desktop session unusable and potentially impacting other applications running on the same host if thread scheduling policies are not strictly enforced by the operating system.
This vulnerability aligns with CWE-835, which describes loops that do not terminate or consume excessive resources, as well as CWE-20 regarding improper input validation where the application fails to adequately sanitize or validate data received from an external source. In terms of offensive security frameworks, this attack vector maps directly to MITRE ATT&CK technique T1499.003, known as Endpoint Denial of Service: Resource Exhaustion via Infinite Loops. The exploitation requires no authentication on the client side but does require that the attacker has control over or can manipulate the network path between the FreeRDP client and the gateway server, such as through a compromised proxy or man-in-the-middle position in an unencrypted HTTP tunnel scenario.
The operational impact of this vulnerability is severe for organizations relying on FreeRDP for remote access infrastructure. A successful exploit does not lead to code execution or data exfiltration but rather causes immediate service disruption. For end-users, this manifests as a frozen graphical interface and high CPU usage that may require manual intervention via task manager or system restart to resolve. For administrators, it presents a challenge in maintaining availability of remote desktop services, particularly if the vulnerability is exploited against multiple clients simultaneously through a compromised gateway, potentially causing widespread outages across an enterprise network segment dependent on FreeRDP connections.
Mitigation strategies primarily involve upgrading the FreeRDP installation to version 3.32.0 or later, where this parsing logic has been corrected to handle malformed headers gracefully without entering infinite loops. In environments where immediate patching is not feasible, administrators should implement strict input filtering at the network perimeter using web application firewalls or proxy servers configured to reject HTTP responses with suspicious Content-Type structures before they reach FreeRDP clients. Additionally, enforcing HTTPS for all RDP gateway connections ensures that attackers cannot easily manipulate response headers in transit unless they have already compromised a trusted internal node. Regular monitoring of CPU usage on client machines can also serve as an early detection mechanism for such resource exhaustion attacks, allowing security teams to isolate affected systems before total service failure occurs.