CVE-2020-15103: 
NixOS vulnerability analysis and mitigation

CVE-2020-15103 affects FreeRDP versions less than or equal to 2.1.2, where an integer overflow vulnerability exists due to missing input sanitation in the rdpegfx channel. The vulnerability was discovered in June 2020 and fixed in version 2.2.0 (GitHub Advisory).

The vulnerability stems from insufficient validation of input rectangles from the server against local surface coordinates. The input rectangles are blindly accepted without proper bounds checking, leading to an integer overflow condition. This can result in invalid length arguments being passed to memcpy operations (GitHub Advisory, Debian Tracker).

When exploited, a malicious server can send crafted data that will cause the FreeRDP client to crash, resulting in a denial of service condition. The vulnerability affects all FreeRDP clients (GitHub Advisory, Ubuntu Security).

The vulnerability can be exploited by a malicious RDP server by sending specially crafted data to a connecting FreeRDP client. The attack vector requires the attacker to control the RDP server that the client connects to (GitHub Advisory).

The primary mitigation is to upgrade to FreeRDP version 2.2.0 or later which contains the fix for this vulnerability. As a temporary workaround, users can disable the affected functionality by stopping the use of command line arguments /gfx, /gfx-h264 and /network:auto (GitHub Advisory, OpenSUSE Security).