CVE-2026-78119CVE-2026-78119

The Nuvoton NPCX eSPI driver parses Target-Attached-Flash (TAF) requests in espi_taf_parse() (drivers/espi/espi_npcx.c), taking the 12-bit length field directly out of the request header in the FLASHRXBUF FIFO. For write and RPMC OP1 requests it copied DIV_ROUND_UP(len, 4) words into struct espi_taf_pckt.src, a fixed 16-word (64-byte) member of a static structure, without ever comparing the length against that buffer or against the negotiated eSPI receive payload size (rx-plsize, 64 bytes on all in-tree NPCX/NPCK SoCs). Both the loop counter and the word count were uint8_t, so the copy ran up to 255 iterations. An eSPI controller that emits a flash request whose header claims a payload larger than the negotiated maximum therefore drives up to 239 32-bit stores past the end of the structure — roughly 956 bytes of out-of-bounds write into .bss — from the eSPI flash receive interrupt handler, while the source reads walk past the end of the 18-word FLASHRXBUF register array into neighbour