CVE-2026-114045
Summary
by MITRE • 10/21/2026
FreeRDP before 3.32.1 contains a heap-based buffer overflow in the server-side rdpsnd channel because an integer wraparound in rdpsnd_server_select_format() DVI_ADPCM block-alignment arithmetic bypasses validation. A malicious RDP client can send two SNDC_FORMATS PDUs with an nBlockAlign too small for nChannels, causing an unbounded heap write during server audio playback, potentially enabling code execution.
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Analysis
by VulDB Data Team • 10/21/2026
The vulnerability identified in FreeRDP versions prior to 3.32.1 represents a critical security flaw within the Remote Desktop Protocol implementation, specifically affecting the server-side handling of the rdpsnd channel responsible for audio streaming. This component is designed to manage sound playback on the remote machine by processing data sent from the client. The core technical deficiency lies in the function rdpsnd_server_select_format(), where an integer wraparound occurs during DVI_ADPCM block-alignment arithmetic calculations. In C-based implementations, signed or unsigned integer overflow can lead to unexpected results when values exceed their maximum representable limits, often resulting in a much smaller positive number than intended. This mathematical error directly bypasses subsequent validation checks that are supposed to ensure data integrity and buffer safety before memory allocation occurs.
The exploitation mechanism relies on the interaction between two specific Protocol Data Units (PDUs) sent by an attacker-controlled RDP client: SNDC_FORMATS messages which define audio format parameters, including channel counts and block alignment values. By carefully crafting these PDUs with a nBlockAlign value that is artificially small relative to the number of channels (nChannels), the malicious actor triggers the integer wraparound condition within the server's processing logic. Because the validation routines rely on arithmetic results derived from this flawed calculation, they fail to detect the discrepancy between the requested buffer size and the actual data requirements. Consequently, when the server attempts to process audio playback for these malformed formats, it allocates a heap buffer that is significantly smaller than what is required by the incoming stream data.
This mismatch leads directly to an unbounded heap write operation during server-side audio processing. As the FreeRDP server processes the maliciously crafted audio packets, it writes data beyond the boundaries of the allocated memory region into adjacent heap structures. Heap-based buffer overflows are particularly dangerous because they allow attackers to corrupt metadata associated with dynamic memory allocations, such as size fields or pointers used by the allocator itself. This corruption can be leveraged to achieve arbitrary code execution on the target system. An attacker who successfully exploits this vulnerability could potentially execute malicious payloads with the privileges of the user running the FreeRDP server process, leading to a complete compromise of the remote desktop session and potentially the underlying operating system if privilege escalation vectors are present in other components.
From an industry standards perspective, this vulnerability aligns closely with CWE-190 (Integer Overflow or Wraparound) as the root cause, which subsequently leads to CWE-787 (Out-of-bounds Write). The exploitation technique involves manipulating protocol-level inputs to bypass security checks, a pattern often associated with ATT&CK Tactic TA0002 (Execution), specifically techniques involving remote services. The ability to send crafted PDUs over the network places this vulnerability within the context of remote code execution via vulnerable applications that handle untrusted input without proper validation.
Mitigation for this issue requires immediate updating of FreeRDP installations to version 3.32.1 or later, where the integer arithmetic in rdpsnd_server_select_format() has been corrected and additional bounds checking has likely been implemented. Organizations relying on remote desktop services should verify their patch levels across all endpoints running affected versions. In environments where updates cannot be applied immediately, network-level controls such as firewalls restricting access to RDP ports from untrusted networks can provide a layer of defense in depth. Furthermore, implementing strict input validation at the application gateway level or using intrusion detection systems capable of identifying anomalous PDU structures may help mitigate exploitation attempts until patches are deployed.