{"id":"CVE-2026-80975","revision":"d1e27d79b5de490d960e8e9aff18b9eb","records":[{"revision":"d1e27d79b5de490d960e8e9aff18b9eb","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-80975","aliases":[],"title":"mfd: qnap-mcu: keep the reply buffer alive past a command timeout","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmfd: qnap-mcu: keep the reply buffer alive past a command timeout\n\nqnap_mcu_exec() publishes an on-stack buffer to the receive path:\n\n\tunsigned char rx[QNAP_MCU_RX_BUFFER_SIZE];\n\t...\n\treply->data = rx;\n\treply->length = length;\n\nand qnap_mcu_receive_buf() writes into it from the serdev receive path,\nwhich runs out of flush_to_ldisc() and is not serialized against\nqnap_mcu_exec() at all. bus_lock cannot cover it, because qnap_mcu_exec()\nholds that mutex across wait_for_completion_timeout().\n\nOn a timeout qnap_mcu_exec() returns with reply->data still pointing at\nits own frame. A reply that arrives late, or an unsolicited message from\nthe MCU, is then written into a stack frame that has been left, corrupting\nwhatever runs next on that stack. The same applies when qnap_mcu_write()\nfails, since that path returns without touching the reply state either.\n\nMove the receive buffer into struct qnap_mcu. It is 37 bytes and the\nstructure is devm_kzalloc()ed, so it lives as long as the driver, and a\nlate write lands in memory that is still valid and is reinitialized by the\nnext command. bus_lock keeps commands from sharing it.\n\nThis deliberately does not clear reply->data or reply->length on the\ntimeout path. Doing so races with qnap_mcu_receive_buf(), which reads both\nafter its\n\n\tif (!reply->length)\n\t\treturn size;\n\ncheck: clearing reply->data gives a NULL dereference, and clearing\nreply->length alone removes the reply->received == reply->length exit\ncondition, so the copy loop runs until the uart chunk is consumed and\noverruns the buffer. Leaving both set keeps the write bounded by\nreply->length, which qnap_mcu_exec() has already checked against\nsizeof(mcu->rx).","state":0,"publishedAt":"2026-09-11T19:42:37.086+00:00","modifiedAt":"2026-10-19T08:45:59.772+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"drivers/mfd/qnap-mcu.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"998f70d1806bb718a7565f350283e4a79c8cbb4b\",\n                            \"lessThan\": \"0b6680e306397097a97767447368221fac753809\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"998f70d1806bb718a7565f350283e4a79c8cbb4b\",\n                            \"lessThan\": \"8391ee06d08845a0a165b5fe679ba326915166b2\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"998f70d1806bb718a7565f350283e4a79c8cbb4b\",\n                            \"lessThan\": \"47504742cea7878ebd1bf1491bbed923df6b90b1\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"drivers/mfd/qnap-mcu.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6.14\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"6.14\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.51\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.4\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/0b6680e306397097a97767447368221fac753809","https://git.kernel.org/stable/c/8391ee06d08845a0a165b5fe679ba326915166b2","https://git.kernel.org/stable/c/47504742cea7878ebd1bf1491bbed923df6b90b1"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-80975","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-80975","identifiers":["CVE-2026-80975"]},"retained":false,"historicalAffected":[]}],"coverage":[]}