Medium [CVE-2026-67306] Out-of-bounds read vulnerability via crafted RDP messages

FreeRDP versions 3.28.0 and earlier contain an out-of-bounds read vulnerability in the RDP6 planar RLE bitmap decoder functions planar_decompress_plane_rle and planar_decompress_plane_rle_only in libfreerdp/codec/planar.c.

Only the 1-byte control byte is bounds-checked; the subsequent 0–15 attacker-declared raw bytes are read without validating that the source buffer contains them.

A malicious or compromised RDP server can send a truncated planar-encoded bitmap or surface update (reachable via both the Bitmap Update PDU and RDPGFX Surface Command paths) that causes the client to read past the end of the source buffer. A flaw was found in FreeRDP.

This can cause the client to read beyond the intended memory buffer, potentially leading to a denial of service (client crash) or the disclosure of sensitive information. Successful exploitation requires user interaction or specific client connection behavior.

An attacker cannot trigger this vulnerability remotely on an arbitrary client system without the client actively initiating an RDP session to a malicious or compromised RDP server. The out-of-bounds read vulnerability is strictly contained within the client application process.

Affected products named by the advisory: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; and 2 more.