CVE-2026-121412 in FreeRDP
Summary
by MITRE • 11/03/2026
FreeRDP from 3.0.0 before 3.32.2 contains an uncontrolled resource consumption vulnerability in the proxy that lets connected clients retain heap memory via intercepted DVC message reassembly. Attackers can declare a large DATA_FIRST length and keep sending fragments without completing the message, growing proxy memory proportional to traffic and degrading service.
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Analysis
by VulDB Data Team • 11/04/2026
The identified vulnerability resides within FreeRDP versions 3.0.0 through 3.32.1, specifically affecting the remote desktop protocol proxy component. This flaw is classified as an uncontrolled resource consumption issue that allows attackers to exhaust system memory resources by manipulating how dynamic virtual channel messages are processed and reassembled. The core technical failure lies in the lack of strict validation or limits on the DATA_FIRST length field during message fragmentation handling. When a client initiates a connection, it can declare an excessively large size for the initial data fragment while intentionally withholding subsequent fragments required to complete the full message structure.
From a technical perspective, the proxy allocates heap memory based on the declared length in the DATA_FIRST packet without verifying whether the remaining segments will actually arrive within a reasonable timeframe or total volume limit. This behavior creates an opportunity for resource exhaustion attacks where malicious actors can keep connections open and continuously send partial fragments. Each incomplete message consumes additional RAM as the system attempts to buffer incoming data awaiting completion, leading to linear memory growth proportional to the number of active fraudulent sessions rather than bounded by actual useful payload size.
The operational impact of this vulnerability is significant for any infrastructure relying on FreeRDP proxies for managing remote desktop connections. Attackers can leverage this flaw to trigger a denial-of-service condition against target systems or network services. By sustaining multiple such incomplete transactions, the proxy process will steadily consume available heap memory until it reaches system limits, potentially causing crashes, service interruptions, or degraded performance for legitimate users sharing the same resources. This type of attack is particularly dangerous in multi-tenant environments where resource isolation may not be strictly enforced at the application layer.
This vulnerability aligns with CWE-400, which describes uncontrolled resource consumption leading to denial-of-service conditions. It also maps to MITRE ATT&CK technique T1499, specifically endpoint denial of service via resource exhaustion methods that target application-level protocols rather than network bandwidth alone. The attack vector is remote and requires authentication or valid connection establishment depending on the specific deployment configuration, making it a viable threat for authenticated adversaries seeking to disrupt availability without necessarily compromising confidentiality or integrity directly.
Mitigation strategies should prioritize upgrading FreeRDP to version 3.32.2 or later where these bounds checking mechanisms have been implemented. In environments where immediate patching is not feasible, administrators can implement network-level rate limiting and connection timeouts to restrict the duration of idle or incomplete sessions. Additionally, configuring resource quotas for proxy processes and monitoring heap usage metrics can help detect anomalous growth patterns indicative of such exploitation attempts before critical system failure occurs.