{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-9728", "assignerOrgId": "e2e69745-5e70-4e92-8431-deb5529a81ad", "state": "PUBLISHED", "assignerShortName": "zephyr", "dateReserved": "2026-05-27T17:11:30.502Z", "datePublished": "2026-08-24T14:28:46.429Z", "dateUpdated": "2026-08-24T14:28:46.429Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad", "shortName": "zephyr", "dateUpdated": "2026-08-24T14:28:46.429Z"}, "title": "TOCTOU race in mbox_send syscall verifier allows userspace to leak kernel memory", "descriptions": [{"lang": "en", "value": "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."}], "affected": [{"vendor": "zephyrproject", "product": "zephyr", "collectionURL": "https://github.com/zephyrproject-rtos/zephyr", "packageName": "zephyr", "defaultStatus": "unaffected", "programFiles": ["drivers/mbox/mbox_handlers.c"], "versions": [{"version": "3.0.0", "status": "affected", "versionType": "semver", "lessThan": "4.4.2"}]}], "references": [{"url": "https://github.com/zephyrproject-rtos/zephyr/commit/ab35eaccec5976f05c196f176d0c32885754496f", "name": "Fix commit", "tags": ["patch"]}, {"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-47q2-w832-7w67", "name": "GHSA-47q2-w832-7w67"}], "metrics": [{"format": "CVSS", "cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:L", "baseScore": 6.4, "baseSeverity": "MEDIUM"}}], "problemTypes": [{"descriptions": [{"lang": "en", "description": "race", "cweId": "CWE-367", "type": "CWE"}]}], "x_generator": {"engine": "cvelib 1.8.0"}}}}

{}

{"affected": [{"affectedData": [{"collectionURL": "https://github.com/zephyrproject-rtos/zephyr", "defaultStatus": "unaffected", "packageName": "zephyr", "product": "zephyr", "programFiles": ["drivers/mbox/mbox_handlers.c"], "vendor": "zephyrproject", "versions": [{"lessThan": "4.4.2", "status": "affected", "version": "3.0.0", "versionType": "semver"}]}], "source": "vulnerabilities@zephyrproject.org"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "id": "CVE-2026-9728", "lastModified": "2026-08-24T15:16:49.010", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "LOCAL", "availabilityImpact": "LOW", "baseScore": 6.4, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 1.1, "impactScore": 4.7, "source": "vulnerabilities@zephyrproject.org", "type": "Secondary"}]}, "published": "2026-08-24T15:16:49.010", "references": [{"source": "vulnerabilities@zephyrproject.org", "url": "https://github.com/zephyrproject-rtos/zephyr/commit/ab35eaccec5976f05c196f176d0c32885754496f"}, {"source": "vulnerabilities@zephyrproject.org", "url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-47q2-w832-7w67"}], "sourceIdentifier": "vulnerabilities@zephyrproject.org", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-367"}], "source": "vulnerabilities@zephyrproject.org", "type": "Secondary"}]}

{}

{}