Information disclosure via truncated RDPGFX planar payload

Summary

FreeRDP is a free implementation of the Remote Desktop Protocol. From 3.21.0 before 3.28.0, FreeRDP clients using the GFX pipeline contain an incomplete fix for CVE-2026-23530 in planar_decompress_plane_rle_only in libfreerdp/codec/planar.c, allowing a malicious RDP server to send a truncated RDPGFX_CMDID_WIRETOSURFACE_1 planar payload that reads one byte past the input buffer. This issue is fixed in version 3.28.0. FreeRDP clients using the Graphics (GFX) pipeline are vulnerable to an out-of-bounds read. A malicious RDP server can exploit this by sending a specially crafted, truncated RDPGFX_CMDID_WIRETOSURFACE_1 planar payload. This can lead to reading one byte beyond the intended buffer, potentially disclosing sensitive information or causing a denial of service. Red Hat severity: Moderate — CVSS 5.4 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L). Weakness: CWE-125. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9. Will not fix / out of support: Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7. Red Hat does not currently list a fixing RHSA for this CVE.