UBUNTU-CVE-2026-121958: High severity ubuntu/freerdp vulnerability

FreeRDP through 3.32.1 has a heap out-of-bounds write in the RDPGFX client because the deletesurface callback truncates surface hash keys to 16 bits, leaving the surface table inconsistent so HashTableGetKeys writes past its allocated key array. A malicious or man-in-the-middle RDP server can exploit this by creating surfaceId 0xFFFF, closing the RDPGFX channel, sending repeated DELETESURFACE PDUs, and then sending ENDFRAME or RESETGRAPHICS.