CVE-2026-55192: FreeRDP: Out-of-bounds read in H.264 YUV-to-RGB conversion due to decoder/surface dimension mismatch
FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.27.0, FreeRDP H.264 decoder backends can return YUV planes sized from the bitstream without comparing the decoded width and height to the RDPGFX surface dimensions used to validate region rectangles. A malicious RDP server can provide an AVC420 or AVC444 bitstream whose decoded frame is smaller than the negotiated surface, causing yuv420contextdecode and the YUV-to-RGB conversion paths to read beyond the decoder-owned planes in libfreerdp/codec/h264.c and the selected H.264 backend. This can disclose client memory or crash the client. This issue is fixed in version 3.27.0.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
FreeRDPto a version that resolves this vulnerability.Fixed in 3.27.0
Event History
Frequently Asked Questions
Which systems are exposed to this issue?
FreeRDP clients using an affected version prior to 3.27.0 are exposed when they connect to a malicious RDP server that sends H.264 AVC420 or AVC444 graphics data. The issue affects H.264 decoder backends and the YUV-to-RGB conversion paths.
What must an attacker control to exploit it?
An attacker must operate or control an RDP server that a vulnerable FreeRDP client connects to. The server must send an H.264 bitstream that decodes to a frame smaller than the negotiated RDPGFX surface dimensions.
What is the impact on a vulnerable client?
The malformed frame can cause FreeRDP to read beyond decoder-owned YUV planes during conversion. This may disclose client memory or crash the client.
What should be done if a client cannot be upgraded immediately?
The provided information identifies version 3.27.0 as the fix. Until it can be deployed, avoid connecting affected FreeRDP clients to untrusted or potentially malicious RDP servers.