MGASA-2021-0522

All FreeRDP clients prior to version 2.4.1 using gateway connections ('/gt:rpc') fail to validate input data. A malicious gateway might allow client memory to be written out of bounds. This issue has been resolved in version 2.4.1. If you are unable to update then use /gt:http rather than /gt:rdp connections if possible or use a direct connection without a gateway. (CVE-2021-41159)

In affected versions a malicious server might trigger out of bound writes in a connected client. Connections using GDI or SurfaceCommands to send graphics updates to the client might send 0 width/height or out of bound rectangles to trigger out of bound writes. With 0 width or heigth the memory allocation will be 0 but the missing bounds checks allow writing to the pointer at this (not allocated) region. This issue has been patched in FreeRDP 2.4.1. (CVE-2021-41160)