{"affected":[{"defaultStatus":"unaffected","ecosystem":"https://github.com/zephyrproject-rtos/zephyr","packageName":"zephyr","product":"zephyr","source":"CNA: zephyr","vendor":"zephyrproject","versions":[{"lessThan":"4.3.2","status":"affected","version":"3.0.0","versionType":"semver"},{"lessThan":"4.4.2","status":"affected","version":"4.4.0","versionType":"semver"}]}],"cveId":"CVE-2026-9728","cwes":["CWE-367"],"description":"The userspace syscall verifier z_vrfy_mbox_send() in drivers/mbox/mbox_handlers.c validated the nested msg->data/msg->size fields by reading them directly out of live userspace memory, and then forwarded the original, still-mutable userspace struct mbox_msg * pointer to z_impl_mbox_send() and the underlying driver. Between the access check and the driver's use of msg->data, the validated pointer could be replaced, leaving a time-of-check/time-of-use window.\n\nOn a system built with CONFIG_USERSPACE, any unprivileged userspace thread may invoke the mbox_send() system call. A second thread sharing the caller's address space can race to overwrite msg->data with a supervisor (kernel) address after the verifier's bounds check has passed but before the driver dereferences it. The driver then reads from the attacker-chosen address in supervisor context (for example memcpy(&data32, msg->data, msg->size) in the NXP mailbox driver, whose bytes are subsequently emitted to the peer mailbox endpoint).\n\nThe impact is a userspace-to-supervisor access-control bypass: disclosure of kernel memory contents (high confidentiality impact), or, for an invalid/unmapped target address, a faulting kernel read causing denial of service. The fix snapshots the entire struct mbox_msg into a kernel-stack copy with k_usermode_from_copy() and validates and forwards that immutable copy, closing the race.","epss":{"date":"2026-11-03","percentile":0.01263,"score":0.0011},"exploits":[],"kev":null,"metrics":[{"score":6.4,"severity":"medium","source":"CNA: zephyr","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:L","version":"3.1"},{"score":6.4,"severity":"medium","source":"NVD: vulnerabilities@zephyrproject.org","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:L","version":"3.1"}],"modifiedAt":1793769547053,"publishedAt":1787581726429,"references":[{"source":"CNA: zephyr","tags":["patch"],"url":"https://github.com/zephyrproject-rtos/zephyr/commit/ab35eaccec5976f05c196f176d0c32885754496f"},{"source":"CNA: zephyr","tags":[],"url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-47q2-w832-7w67"},{"source":"vulnerabilities@zephyrproject.org","tags":[],"url":"https://github.com/zephyrproject-rtos/zephyr/commit/ab35eaccec5976f05c196f176d0c32885754496f"},{"source":"vulnerabilities@zephyrproject.org","tags":[],"url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-47q2-w832-7w67"}],"remediation":[{"kind":"fix","source":"CNA: zephyr","text":"The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.","url":"https://github.com/zephyrproject-rtos/zephyr/commit/ab35eaccec5976f05c196f176d0c32885754496f"}],"revision":"f84c1e2573b8dd7fe1a06fa223d7bc555fe28a69808ddd99672ef4872ec21ba3","sources":[{"modifiedAt":1793768389294,"name":"CNA: zephyr","retrievedAt":1793769143950,"url":"https://www.cve.org/CVERecord?id=CVE-2026-9728"},{"modifiedAt":1793769547053,"name":"NVD","retrievedAt":1793772958628,"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-9728"},{"modifiedAt":null,"name":"FIRST EPSS","retrievedAt":1793769146087,"url":"https://api.first.org/data/v1/epss?cve=CVE-2026-9728"}],"ssvc":{"assessedAt":1787684787362,"automatable":"no","exploitation":"none","source":"ADP: CISA-ADP","technicalImpact":"partial"},"status":"published","title":"TOCTOU race in mbox_send syscall verifier allows userspace to leak kernel memory","updatedAt":1793772958628}