{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-40026",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2025-40026"
  ],
  "published": "2025-10-28T09:32:47Z",
  "summary": "KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Don't (re)check L1 intercepts when completing userspace I/O\n\nWhen completing emulation of instruction that generated a userspace exit\nfor I/O, don't recheck L1 intercepts as KVM has already finished that\nphase of instruction execution, i.e. has already committed to allowing L2\nto perform I/O.  If L1 (or host userspace) modifies the I/O permission\nbitmaps during the exit to userspace,  KVM will treat the access as being\nintercepted despite already having emulated the I/O access.\n\nPivot on EMULTYPE_NO_DECODE to detect that KVM is completing emulation.\nOf the three users of EMULTYPE_NO_DECODE, only complete_emulated_io() (the\nintended \"recipient\") can reach the code in question.  gp_interception()'s\nuse is mutually exclusive with is_guest_mode(), and\ncomplete_emulated_insn_gp() unconditionally pairs EMULTYPE_NO_DECODE with\nEMULTYPE_SKIP.\n\nThe bad behavior was detected by a syzkaller program that toggles port I/O\ninterception during the userspace I/O exit, ultimately resulting in a WARN\non vcpu->arch.pio.count being non-zero due to KVM no completing emulation\nof the I/O instruction.\n\n  WARNING: CPU: 23 PID: 1083 at arch/x86/kvm/x86.c:8039 emulator_pio_in_out+0x154/0x170 [kvm]\n  Modules linked in: kvm_intel kvm irqbypass\n  CPU: 23 UID: 1000 PID: 1083 Comm: repro Not tainted 6.16.0-rc5-c1610d2d66b1-next-vm #74 NONE\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n  RIP: 0010:emulator_pio_in_out+0x154/0x170 [kvm]\n  PKRU: 55555554\n  Call Trace:\n   <TASK>\n   kvm_fast_pio+0xd6/0x1d0 [kvm]\n   vmx_handle_exit+0x149/0x610 [kvm_intel]\n   kvm_arch_vcpu_ioctl_run+0xda8/0x1ac0 [kvm]\n   kvm_vcpu_ioctl+0x244/0x8c0 [kvm]\n   __x64_sys_ioctl+0x8a/0xd0\n   do_syscall_64+0x5d/0xc60\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n   </TASK>",
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.157",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-40026"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/a908eca437789589dd4624da428614c1275064dc"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/00338255bb1f422642fb2798ebe92e93b6e4209b"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/e0ce3ed1048a47986d15aef1a98ebda25560d257"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ba35a5d775799ce5ad60230be97336f2fefd518e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/3d3abf3f7e8b1abb082070a343de82d7efc80523"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/e7177c7e32cb806f348387b7f4faafd4a5b32054"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/3a062a5c55adc5507600b9ae6d911e247e2f1d6e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/7366830642505683bbe905a2ba5d18d6e4b512b8"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/e750f85391286a4c8100275516973324b621a269"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z"
  }
}