CVE-2026-87038

Что произошло

The user-mode verification handler for the i3c_transfer() system call, z_vrfy_i3c_transfer() in drivers/i3c/i3c_handlers.c, validated the caller-supplied struct i3c_device_desc in place instead of snapshotting it. It confirmed only that the descriptor was readable by the calling thread (K_SYSCALL_MEMORY_READ()), read target->bus once to check it with K_SYSCALL_OBJ(), and then passed the caller's live pointer down. The implementation z_impl_i3c_transfer() re-reads target->bus from that user memory and dispatches through it as DEVICE_API_GET(i3c, target->bus)->i3c_xfers(...), so the bus that was validated is not necessarily the bus that is used. DEVICE_API_GET() performs no runtime type check outside CONFIG_DEVICE_API_ASSERT builds. On a build with CONFIG_USERSPACE and an I3C controller driver, a user thread that has been granted an I3C device object can exploit this with a second thread in the same memory domain: one thread calls i3c_transfer() while the other rewrites the bus field of the descriptor. The window between the check and the use spans the num_msgs validation, the message-array access check, a stack VLA allocation and a memcpy() of up to 32 struct i3c_msg, so the race is repeatable and can simply be retried until it lands. When the substitution succeeds, the kernel dereferences an attacker-chosen pointer as a struct device, loads a function pointer from the attacker-controlled api table and calls it in supervisor mode with attacker-influenced arguments. This yields kernel-mode code execution from an unprivileged user thread — a complete escape of the userspace memory-protection sandbox; lesser outcomes are an arbitrary two-level kernel read or a kernel fault. Builds without CONFIG_USERSPACE, or without an I3C driver, are unaffected. The fix copies the descriptor into a kernel-stack local with k_usermode_from_copy(), validates the bus in that copy, and dispatches on the copy, so the validated value is provably the value used.

Что делать

dpkg-query -W -f='${Package}	${Version}\n'

rpm -qa --qf '%{NAME}\t%{VERSION}-%{RELEASE}\n'

Get-HotFix | Select-Object HotFixID, InstalledOn

Продукты и затронутые версии

{
  "status": "affected",
  "version": "3.2.0",
  "lessThan": "4.3.2",
  "versionType": "semver"
}

{
  "status": "affected",
  "version": "4.4.0",
  "lessThan": "4.5.0",
  "versionType": "semver"
}

CVSS: оценки и векторы

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Источники и ссылки

{
  "cwes": [
    "cve",
    "nvd"
  ],
  "title": {
    "source": "cve",
    "received_at": "2026-11-04T06:19:42.236813+00:00"
  },
  "scores": [
    "cve",
    "nvd"
  ],
  "status": {
    "source": "cve",
    "received_at": "2026-11-04T06:19:42.236813+00:00"
  },
  "affected": [
    "cve"
  ],
  "published": {
    "source": "cve",
    "received_at": "2026-11-04T06:19:42.236813+00:00"
  },
  "solutions": [],
  "references": [
    "cve",
    "nvd"
  ],
  "description": {
    "source": "cve",
    "received_at": "2026-11-04T06:19:42.236813+00:00"
  },
  "workarounds": [],
  "configurations": []
}

Хронология записи

1. Появились сведения об исправлении04.11.2026, 09:19
2. Опубликована04.11.2026, 09:19

Личная заметка и статус

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