{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "In the Linux kernel, the following vulnerability has been resolved:  mfd: qnap-mcu: keep the reply buffer alive past a command timeout  qnap_mcu_exec() publishes an on-stack buffer to the receive path:  \tunsigned char rx[QNAP_MCU_RX_BUFFER_SIZE]; \t... \treply-\u003edata = rx; \treply-\u003elength = length;  and qnap_mcu_receive_buf() writes into it from the serdev receive path, which runs out of flush_to_ldisc() and is not serialized against qnap_mcu_exec() at all. bus_lock cannot cover it, because qnap_mcu_exec() holds that mutex across wait_for_completion_timeout().  On a timeout qnap_mcu_exec() returns with reply-\u003edata still pointing at its own frame. A reply that arrives late, or an unsolicited message from the MCU, is then written into a stack frame that has been left, corrupting whatever runs next on that stack. The same applies when qnap_mcu_write() fails, since that path returns without touching the reply state either.  Move the receive buffer into struct qnap_mcu. It is 37 bytes and the structure is devm_kzalloc()ed, so it lives as long as the driver, and a late write lands in memory that is still valid and is reinitialized by the next command. bus_lock keeps commands from sharing it.  This deliberately does not clear reply-\u003edata or reply-\u003elength on the timeout path. Doing so races with qnap_mcu_receive_buf(), which reads both after its  \tif (!reply-\u003elength) \t\treturn size;  check: clearing reply-\u003edata gives a NULL dereference, and clearing reply-\u003elength alone removes the reply-\u003ereceived == reply-\u003elength exit condition, so the copy loop runs until the uart chunk is consumed and overruns the buffer. Leaving both set keeps the write bounded by reply-\u003elength, which qnap_mcu_exec() has already checked against sizeof(mcu-\u003erx).",
  "id": "DEBIAN-CVE-2026-80975",
  "modified": "2026-09-14T08:47:36.811453425Z",
  "published": "2026-09-11T20:19:03.763Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-80975"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "upstream": [
    "CVE-2026-80975"
  ]
}