We have identified a new heap buffer overflow vulnerability in Mediatek’s baseband implementation. The vulnerability can be exploited to achieve arbitrary code execution in the baseband runtime. The vulnerability we are disclosing in this advisory affected a wide range of Mediatek devices, including phones on the newest chipsets (Dimensity 700, 1000, etc). The July 2022 issue of the Mediatek Security Bulletin contains this vulnerability as CVE-2022-21744. Vulnerability Details The GPRS Packet Neighbour Cell Data (PNCD) message is an optional message sent by the network on the PACCH to provide system information required for initial access in a neighbouring cell. In the case of the MediaTek baseband firmware, this message is processed in the FDD_rmpc_mac_rmpc_pncd_ind_hdlr function.