Pgm

CVE-2026-54995 — Microsoft Windows Reliable Multicast Transport Driver Integer Underflow 1. Overview A vulnerability exists in the Windows Reliable Multicast Transport Driver (rmcast.sys) that implements the Pragmatic General Multicast (PGM) protocol. When processing incoming ODATA packets for a Forward Error Correction (FEC) group, the driver’s PgmHandleNewData function can decrement a parity packet counter past zero, causing an unsigned byte to underflow from 0 to 255. This corrupted counter subsequently causes out-of-bounds memory access when the driver attempts FEC decoding with an impossibly large parity count. An unauthenticated remote attacker can send specially crafted PGM multicast packets to a system running a PGM receiver application, potentially achieving kernel-level code execution. Microsoft addressed this vulnerability in the July 2026 security update. ...