{"id":"CVE-2026-19185","aliases":["EUVD-2026-92286","GHSA-pcrr-29j7-8w57"],"status":"published","title":"Unvalidated user-supplied buffer pointers in the I3C do_ccc system call handler allow kernel memory read/write from user mode","description":"The system-call verifier for i3c_do_ccc() in drivers/i3c/i3c_handlers.c validated the outer struct i3c_ccc_payload, the broadcast ccc.data buffer and the targets.payloads[] array, but did not validate the per-target data buffers those array elements point at. Each struct i3c_ccc_target_payload carries its own data pointer and data_len, and neither was passed through K_SYSCALL_MEMORY() before the payload was handed to z_impl_i3c_do_ccc() and on to the controller driver. The verifier also operated on the caller's live structure rather than a snapshot, so validated fields could be changed by a second user thread between the check and the driver's use — unlike the sibling z_vrfy_i3c_transfer(), which has always copied its message array first.\n\nThe defect is only present in CONFIG_USERSPACE builds, where drivers/i3c/i3c_handlers.c is compiled. An unprivileged user-mode thread that has been granted access to the I3C controller device object — the ordinary way an application lets a user thread talk to I3C peripherals — can issue a direct CCC whose target payload data pointer names an arbitrary kernel address. Controller drivers dereference that pointer directly (for example drivers/i3c/i3c_mcux.c, drivers/i3c/i3c_cdns.c, drivers/i3c/i3c_stm32.c, drivers/i3c/i3c_npcx.c), using rnw to decide direction.\n\nA read CCC therefore causes the kernel-mode driver to write bus-received bytes into an attacker-chosen kernel address for an attacker-chosen length, and a write CCC transmits kernel memory out onto the I3C bus. The result is an out-of-bounds kernel write plus a kernel memory disclosure, i.e. escalation from a user-mode thread to supervisor privilege, defeating the isolation CONFIG_USERSPACE is meant to provide.\n\nThe fix introduces copy_ccc_and_do(), which snapshots the payload, copies the target array into kernel memory with k_usermode_alloc_from_copy() (bounding num_targets to fewer than 32), validates each per-target buffer with K_SYSCALL_MEMORY() according to rnw, and copies the driver-written num_xfer and err fields back to the caller.","severity":{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00168,"percentile":0.06083,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-822"],"published":"2026-10-05T08:06:29Z","modified":"2026-11-04T05:00:33Z","products":[{"vendor":"zephyrproject","product":"zephyr"},{"vendor":"zephyrproject-rtos","product":"zephyr"}],"references":[{"url":"https://github.com/zephyrproject-rtos/zephyr/commit/35562f22f40c6d2f31969a31f0a4902e5b067f27","tags":["patch","fix"]},{"url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-pcrr-29j7-8w57","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/19xxx/CVE-2026-19185.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-19185","tags":["advisory"]},{"url":"https://github.com/zephyrproject-rtos/zephyr","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-19185","title":"Unvalidated user-supplied buffer pointers in the I3C do_ccc system call handler allow kernel memory read/write from user mode","description":"The system-call verifier for i3c_do_ccc() in drivers/i3c/i3c_handlers.c validated the outer struct i3c_ccc_payload, the broadcast ccc.data buffer and the targets.payloads[] array, but did not validate the per-target data buffers those array elements point at. Each struct i3c_ccc_target_payload carries its own data pointer and data_len, and neither was passed through K_SYSCALL_MEMORY() before the payload was handed to z_impl_i3c_do_ccc() and on to the controller driver. The verifier also operated on the caller's live structure rather than a snapshot, so validated fields could be changed by a second user thread between the check and the driver's use — unlike the sibling z_vrfy_i3c_transfer(), which has always copied its message array first.\n\nThe defect is only present in CONFIG_USERSPACE builds, where drivers/i3c/i3c_handlers.c is compiled. An unprivileged user-mode thread that has been granted access to the I3C controller device object — the ordinary way an application lets a user thread talk to I3C peripherals — can issue a direct CCC whose target payload data pointer names an arbitrary kernel address. Controller drivers dereference that pointer directly (for example drivers/i3c/i3c_mcux.c, drivers/i3c/i3c_cdns.c, drivers/i3c/i3c_stm32.c, drivers/i3c/i3c_npcx.c), using rnw to decide direction.\n\nA read CCC therefore causes the kernel-mode driver to write bus-received bytes into an attacker-chosen kernel address for an attacker-chosen length, and a write CCC transmits kernel memory out onto the I3C bus. The result is an out-of-bounds kernel write plus a kernel memory disclosure, i.e. escalation from a user-mode thread to supervisor privilege, defeating the isolation CONFIG_USERSPACE is meant to provide.\n\nThe fix introduces copy_ccc_and_do(), which snapshots the payload, copies the target array into kernel memory with k_usermode_alloc_from_copy() (bounding num_targets to fewer than 32), validates each per-target buffer with K_SYSCALL_MEMORY() according to rnw, and copies the driver-written num_xfer and err fields back to the caller.","status":"published","published":"2026-10-05T08:06:29.874Z","modified":"2026-11-04T05:00:33.963Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-822"],"updated_at":"2026-11-04T05:21:48.223566Z"}],"euvd":[{"id":"EUVD-2026-92286","description":"The system-call verifier for i3c_do_ccc() in drivers/i3c/i3c_handlers.c validated the outer struct i3c_ccc_payload, the broadcast ccc.data buffer and the targets.payloads[] array, but did not validate the per-target data buffers those array elements point at. Each struct i3c_ccc_target_payload carries its own data pointer and data_len, and neither was passed through K_SYSCALL_MEMORY() before the payload was handed to z_impl_i3c_do_ccc() and on to the controller driver. The verifier also operated on the caller's live structure rather than a snapshot, so validated fields could be changed by a second user thread between the check and the driver's use — unlike the sibling z_vrfy_i3c_transfer(), which has always copied its message array first.\n\nThe defect is only present in CONFIG_USERSPACE builds, where drivers/i3c/i3c_handlers.c is compiled. An unprivileged user-mode thread that has been granted access to the I3C controller device object — the ordinary way an application lets a user thread talk to I3C peripherals — can issue a direct CCC whose target payload data pointer names an arbitrary kernel address. Controller drivers dereference that pointer directly (for example drivers/i3c/i3c_mcux.c, drivers/i3c/i3c_cdns.c, drivers/i3c/i3c_stm32.c, drivers/i3c/i3c_npcx.c), using rnw to decide direction.\n\nA read CCC therefore causes the kernel-mode driver to write bus-received bytes into an attacker-chosen kernel address for an attacker-chosen length, and a write CCC transmits kernel memory out onto the I3C bus. The result is an out-of-bounds kernel write plus a kernel memory disclosure, i.e. escalation from a user-mode thread to supervisor privilege, defeating the isolation CONFIG_USERSPACE is meant to provide.\n\nThe fix introduces copy_ccc_and_do(), which snapshots the payload, copies the target array into kernel memory with k_usermode_alloc_from_copy() (bounding num_targets to fewer than 32), validates each per-target buffer with K_SYSCALL_MEMORY() according to rnw, and copies the driver-written num_xfer and err fields back to the caller.","status":"published","published":"2026-10-05T08:06:29Z","modified":"2026-11-04T05:00:33Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-04T07:00:56.720215Z"}],"nvd":[{"id":"CVE-2026-19185","description":"The system-call verifier for i3c_do_ccc() in drivers/i3c/i3c_handlers.c validated the outer struct i3c_ccc_payload, the broadcast ccc.data buffer and the targets.payloads[] array, but did not validate the per-target data buffers those array elements point at. Each struct i3c_ccc_target_payload carries its own data pointer and data_len, and neither was passed through K_SYSCALL_MEMORY() before the payload was handed to z_impl_i3c_do_ccc() and on to the controller driver. The verifier also operated on the caller's live structure rather than a snapshot, so validated fields could be changed by a second user thread between the check and the driver's use — unlike the sibling z_vrfy_i3c_transfer(), which has always copied its message array first.\n\nThe defect is only present in CONFIG_USERSPACE builds, where drivers/i3c/i3c_handlers.c is compiled. An unprivileged user-mode thread that has been granted access to the I3C controller device object — the ordinary way an application lets a user thread talk to I3C peripherals — can issue a direct CCC whose target payload data pointer names an arbitrary kernel address. Controller drivers dereference that pointer directly (for example drivers/i3c/i3c_mcux.c, drivers/i3c/i3c_cdns.c, drivers/i3c/i3c_stm32.c, drivers/i3c/i3c_npcx.c), using rnw to decide direction.\n\nA read CCC therefore causes the kernel-mode driver to write bus-received bytes into an attacker-chosen kernel address for an attacker-chosen length, and a write CCC transmits kernel memory out onto the I3C bus. The result is an out-of-bounds kernel write plus a kernel memory disclosure, i.e. escalation from a user-mode thread to supervisor privilege, defeating the isolation CONFIG_USERSPACE is meant to provide.\n\nThe fix introduces copy_ccc_and_do(), which snapshots the payload, copies the target array into kernel memory with k_usermode_alloc_from_copy() (bounding num_targets to fewer than 32), validates each per-target buffer with K_SYSCALL_MEMORY() according to rnw, and copies the driver-written num_xfer and err fields back to the caller.","status":"published","published":"2026-10-05T09:17:13.077Z","modified":"2026-11-04T05:18:47.637Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-822"],"updated_at":"2026-11-04T06:53:22.975398Z"}],"osv":[{"id":"CVE-2026-19185","title":"Unvalidated user-supplied buffer pointers in the I3C do_ccc system call handler allow kernel memory read/write from user mode","description":"The system-call verifier for i3c_do_ccc() in drivers/i3c/i3c_handlers.c validated the outer struct i3c_ccc_payload, the broadcast ccc.data buffer and the targets.payloads[] array, but did not validate the per-target data buffers those array elements point at. Each struct i3c_ccc_target_payload carries its own data pointer and data_len, and neither was passed through K_SYSCALL_MEMORY() before the payload was handed to z_impl_i3c_do_ccc() and on to the controller driver. The verifier also operated on the caller's live structure rather than a snapshot, so validated fields could be changed by a second user thread between the check and the driver's use — unlike the sibling z_vrfy_i3c_transfer(), which has always copied its message array first.\n\nThe defect is only present in CONFIG_USERSPACE builds, where drivers/i3c/i3c_handlers.c is compiled. An unprivileged user-mode thread that has been granted access to the I3C controller device object — the ordinary way an application lets a user thread talk to I3C peripherals — can issue a direct CCC whose target payload data pointer names an arbitrary kernel address. Controller drivers dereference that pointer directly (for example drivers/i3c/i3c_mcux.c, drivers/i3c/i3c_cdns.c, drivers/i3c/i3c_stm32.c, drivers/i3c/i3c_npcx.c), using rnw to decide direction.\n\nA read CCC therefore causes the kernel-mode driver to write bus-received bytes into an attacker-chosen kernel address for an attacker-chosen length, and a write CCC transmits kernel memory out onto the I3C bus. The result is an out-of-bounds kernel write plus a kernel memory disclosure, i.e. escalation from a user-mode thread to supervisor privilege, defeating the isolation CONFIG_USERSPACE is meant to provide.\n\nThe fix introduces copy_ccc_and_do(), which snapshots the payload, copies the target array into kernel memory with k_usermode_alloc_from_copy() (bounding num_targets to fewer than 32), validates each per-target buffer with K_SYSCALL_MEMORY() according to rnw, and copies the driver-written num_xfer and err fields back to the caller.","status":"published","published":"2026-10-05T08:06:29.874Z","modified":"2026-11-05T03:31:26.881750934Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-822"],"updated_at":"2026-11-05T07:12:28.867005Z"}]}}