CVE-2026-110829 in FreeRDP
Summary
by MITRE • 10/15/2026
FreeRDP versions from 3.0.0 before 3.32.0 contain a null pointer dereference in the rdpsnd channel when a fragment sets CHANNEL_FLAG_LAST without CHANNEL_FLAG_FIRST. A malicious RDP server can send a malformed rdpsnd PDU on a fresh channel to crash the client and cause denial of service.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified within FreeRDP versions ranging from 3.0.0 up to, but not including, version 3.32.0 represents a critical memory safety flaw located in the remote desktop sound (rdpsnd) channel implementation. This specific defect is classified as a null pointer dereference, which corresponds directly to CWE-476 in the Common Weakness Enumeration taxonomy. The root cause of this issue lies in the handling of protocol data units during the initialization phase of an audio stream session. Specifically, the vulnerability triggers when a client receives a fragment that asserts the CHANNEL_FLAG_LAST bit without having previously established the CHANNEL_FLAG_FIRST bit on a fresh channel instance. In standard RDP operation, these flags are used to delineate message boundaries and ensure proper state management for multi-part messages. The absence of the FIRST flag indicates an incomplete or malformed sequence, yet the subsequent presence of the LAST flag suggests the end of such a fragment.
From a technical perspective, the flaw arises because the rdpsnd channel handler fails to validate the integrity of the channel state before attempting to process the incoming data structure associated with the audio stream. When a server sends this specific combination of flags on a newly opened or reset channel, the internal pointers required for processing the sound data remain uninitialized or null due to skipped initialization steps that are normally triggered by the FIRST flag. Consequently, when the application attempts to access memory addresses relative to these undefined pointers, it results in an immediate segmentation fault. This behavior is consistent with CWE-476 and highlights a failure in input validation where the software does not adequately verify preconditions before executing operations on potentially invalid data structures.
The operational impact of this vulnerability is primarily focused on availability rather than confidentiality or integrity. A malicious RDP server can exploit this condition by crafting and transmitting a specially crafted rdpsnd PDU to trigger the null pointer dereference. Upon receiving this malformed packet, the FreeRDP client process will abruptly terminate due to the unhandled exception caused by accessing invalid memory. This results in an immediate denial of service for the user attempting to connect via Remote Desktop Protocol. While the primary effect is a crash, such instability can also disrupt ongoing workflows and potentially lead to data loss if unsaved work was present at the time of termination. The attack vector requires network access to interact with the vulnerable RDP server component, placing it within the context of remote code execution attempts that degrade into denial-of-service scenarios as defined by MITRE ATT&CK technique T1499, specifically endpoint denial of service via application crashes.
Mitigation strategies for this vulnerability involve updating the FreeRDP installation to version 3.32.0 or later, where the developers have implemented proper checks to ensure that channel state is correctly initialized before processing fragments marked as final without a preceding start marker. Administrators should also consider implementing network-level authentication and restricting RDP access to trusted networks only to reduce the attack surface exposed to untrusted servers. Additionally, deploying intrusion detection systems capable of identifying anomalous RDP traffic patterns may provide an additional layer of defense against exploitation attempts targeting this specific memory corruption flaw until patches are fully deployed across all endpoints.