CVE-2026-114045 Overview
CVE-2026-114045 is a heap-based buffer overflow [CWE-122] in FreeRDP server implementations before version 3.32.1. The flaw resides in the server-side rdpsnd audio channel, where an integer wraparound in rdpsnd_server_select_format() bypasses block-alignment validation for DVI_ADPCM formats. A malicious Remote Desktop Protocol (RDP) client can transmit two crafted SNDC_FORMATS Protocol Data Units (PDUs) with an nBlockAlign value smaller than nChannels, triggering an unbounded heap write during server audio playback. Successful exploitation may lead to arbitrary code execution on the RDP server process.
Critical Impact
A low-privileged RDP client can corrupt server heap memory via malformed audio format PDUs, potentially achieving remote code execution on the FreeRDP server.
Affected Products
- FreeRDP versions prior to 3.32.1
- Server-side applications linking the FreeRDP rdpsnd server channel
- Downstream projects embedding vulnerable FreeRDP server libraries
Discovery Timeline
- 2026-10-21 - CVE-2026-114045 published to the National Vulnerability Database (NVD)
- 2026-10-22 - Last updated in NVD database
Technical Details for CVE-2026-114045
Vulnerability Analysis
The defect lives in rdpsnd_server_select_format(), the FreeRDP routine that validates audio format descriptors advertised by connecting RDP clients. For DVI_ADPCM compressed audio, the function computes an expected block-alignment value using arithmetic that can wrap around when attacker-controlled fields nBlockAlign and nChannels are chosen adversarially. The wraparound causes the validation check to succeed on values that are logically invalid.
Once the malformed format descriptor is accepted and cached, subsequent audio playback uses the attacker-controlled block alignment to size and index heap buffers. The resulting write operation exceeds the allocated chunk, corrupting adjacent heap metadata and application data. Because the overflow length and content are influenced by the client, exploitation primitives extend beyond denial of service toward arbitrary write and potential code execution.
Root Cause
The root cause is unsafe integer arithmetic combined with missing invariants on nBlockAlign relative to nChannels. The validation does not reject block alignments smaller than the per-channel sample size, allowing a wrapped intermediate value to pass the bounds check. This is a classic integer wraparound feeding a heap-based buffer overflow [CWE-122].
Attack Vector
Exploitation requires network reachability to a FreeRDP-based server and the ability to complete the RDP handshake far enough to open the rdpsnd static virtual channel. The attacker sends two SNDC_FORMATS PDUs containing a DVI_ADPCM format entry with crafted nBlockAlign and nChannels values. When the server initiates audio playback and processes samples under the malformed format, the oversized write corrupts the heap in the server process context.
No public proof-of-concept exploit is listed in the enriched data. Technical details are described in the FreeRDP GitHub Security Advisory and the VulnCheck Advisory on FreeRDP.
Detection Methods for CVE-2026-114045
Indicators of Compromise
- RDP server process crashes with heap corruption signatures during or shortly after rdpsnd channel negotiation.
- Multiple SNDC_FORMATS PDUs from a single client within one session, especially with DVI_ADPCM format entries containing anomalously small nBlockAlign values.
- Unexpected child processes or outbound connections spawned by FreeRDP server binaries following RDP sessions.
Detection Strategies
- Inspect RDP traffic for rdpsnd channel messages where nBlockAlign < nChannels in advertised format headers.
- Enable AddressSanitizer or heap hardening features in test environments to surface the overflow during fuzzing of the rdpsnd server path.
- Correlate server crash telemetry with inbound RDP sessions to identify repeat offenders.
Monitoring Recommendations
- Forward RDP server logs and crash dumps to a centralized data lake for behavioral analysis across sessions.
- Alert on repeated RDP channel renegotiations or format advertisement anomalies from the same source.
- Baseline normal rdpsnd format negotiations and flag statistical outliers for review.
How to Mitigate CVE-2026-114045
Immediate Actions Required
- Upgrade all FreeRDP server deployments to version 3.32.1 or later.
- Audit downstream products and container images for embedded FreeRDP server libraries and update them.
- Restrict inbound RDP exposure to trusted networks and require VPN or zero-trust access for remote users.
Patch Information
The FreeRDP project addressed the issue in release 3.32.1 by correcting the block-alignment validation in rdpsnd_server_select_format() to prevent integer wraparound and to enforce the invariant that nBlockAlign must accommodate nChannels. Refer to the FreeRDP GitHub Security Advisory for the fix commit and backport guidance.
Workarounds
- Disable the rdpsnd static virtual channel in server configuration where audio redirection is not required.
- Place FreeRDP servers behind an RDP gateway or proxy that enforces client authentication before channel negotiation.
- Apply network segmentation to limit which clients can reach FreeRDP server endpoints.
# Configuration example: disable rdpsnd channel on FreeRDP server
freerdp-shadow-cli /port:3389 -audio-input -audio-output
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
