{
"schema_version": "1.6.1",
"id": "RPI-CVE-2026-23005",
"modified": "2026-10-07T17:22:01Z",
"upstream": [
"CVE-2026-23005"
],
"published": "2026-01-25T14:36:48Z",
"summary": "x86/fpu: Clear XSTATE_BV[i] in guest XSAVE state whenever XFD[i]=1",
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/fpu: Clear XSTATE_BV[i] in guest XSAVE state whenever XFD[i]=1\n\nWhen loading guest XSAVE state via KVM_SET_XSAVE, and when updating XFD in\nresponse to a guest WRMSR, clear XFD-disabled features in the saved (or to\nbe restored) XSTATE_BV to ensure KVM doesn't attempt to load state for\nfeatures that are disabled via the guest's XFD. Because the kernel\nexecutes XRSTOR with the guest's XFD, saving XSTATE_BV[i]=1 with XFD[i]=1\nwill cause XRSTOR to #NM and panic the kernel.\n\nE.g. if fpu_update_guest_xfd() sets XFD without clearing XSTATE_BV:\n\n ------------[ cut here ]------------\n WARNING: arch/x86/kernel/traps.c:1524 at exc_device_not_available+0x101/0x110, CPU#29: amx_test/848\n Modules linked in: kvm_intel kvm irqbypass\n CPU: 29 UID: 1000 PID: 848 Comm: amx_test Not tainted 6.19.0-rc2-ffa07f7fd437-x86_amx_nm_xfd_non_init-vm #171 NONE\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n RIP: 0010:exc_device_not_available+0x101/0x110\n Call Trace:\n \n asm_exc_device_not_available+0x1a/0x20\n RIP: 0010:restore_fpregs_from_fpstate+0x36/0x90\n switch_fpu_return+0x4a/0xb0\n kvm_arch_vcpu_ioctl_run+0x1245/0x1e40 [kvm]\n kvm_vcpu_ioctl+0x2c3/0x8f0 [kvm]\n __x64_sys_ioctl+0x8f/0xd0\n do_syscall_64+0x62/0x940\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n \n ---[ end trace 0000000000000000 ]---\n\nThis can happen if the guest executes WRMSR(MSR_IA32_XFD) to set XFD[18] = 1,\nand a host IRQ triggers kernel_fpu_begin() prior to the vmexit handler's\ncall to fpu_update_guest_xfd().\n\nand if userspace stuffs XSTATE_BV[i]=1 via KVM_SET_XSAVE:\n\n ------------[ cut here ]------------\n WARNING: arch/x86/kernel/traps.c:1524 at exc_device_not_available+0x101/0x110, CPU#14: amx_test/867\n Modules linked in: kvm_intel kvm irqbypass\n CPU: 14 UID: 1000 PID: 867 Comm: amx_test Not tainted 6.19.0-rc2-2dace9faccd6-x86_amx_nm_xfd_non_init-vm #168 NONE\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n RIP: 0010:exc_device_not_available+0x101/0x110\n Call Trace:\n \n asm_exc_device_not_available+0x1a/0x20\n RIP: 0010:restore_fpregs_from_fpstate+0x36/0x90\n fpu_swap_kvm_fpstate+0x6b/0x120\n kvm_load_guest_fpu+0x30/0x80 [kvm]\n kvm_arch_vcpu_ioctl_run+0x85/0x1e40 [kvm]\n kvm_vcpu_ioctl+0x2c3/0x8f0 [kvm]\n __x64_sys_ioctl+0x8f/0xd0\n do_syscall_64+0x62/0x940\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n \n ---[ end trace 0000000000000000 ]---\n\nThe new behavior is consistent with the AMX architecture. Per Intel's SDM,\nXSAVE saves XSTATE_BV as '0' for components that are disabled via XFD\n(and non-compacted XSAVE saves the initial configuration of the state\ncomponent):\n\n If XSAVE, XSAVEC, XSAVEOPT, or XSAVES is saving the state component i,\n the instruction does not generate #NM when XCR0[i] = IA32_XFD[i] = 1;\n instead, it operates as if XINUSE[i] = 0 (and the state component was\n in its initial state): it saves bit i of XSTATE_BV field of the XSAVE\n header as 0; in addition, XSAVE saves the initial configuration of the\n state component (the other instructions do not save state component i).\n\nAlternatively, KVM could always do XRSTOR with XFD=0, e.g. by using\na constant XFD based on the set of enabled features when XSAVEing for\na struct fpu_guest. However, having XSTATE_BV[i]=1 for XFD-disabled\nfeatures can only happen in the above interrupt case, or in similar\nscenarios involving preemption on preemptible kernels, because\nfpu_swap_kvm_fpstate()'s call to save_fpregs_to_fpstate() saves the\noutgoing FPU state with the current XFD; and that is (on all but the\nfirst WRMSR to XFD) the guest XFD.\n\nTherefore, XFD can only go out of sync with XSTATE_BV in the above\ninterrupt case, or in similar scenarios involving preemption on\npreemptible kernels, and it we can consider it (de facto) part of KVM\nABI that KVM_GET_XSAVE returns XSTATE_BV[i]=0 for XFD-disabled features.\n\n[Move clea\n---truncated---",
"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": "6.1.162",
"compiled_filter": false
}
}
}
}
],
"references": [
{
"type": "ADVISORY",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-23005"
},
{
"type": "FIX",
"url": "https://git.kernel.org/stable/c/b5995c01ba53d84182ecb9492fc4d91cfe8a362d"
},
{
"type": "FIX",
"url": "https://git.kernel.org/stable/c/1e2848bda819af569dfe7ab186223855e092a2cb"
},
{
"type": "FIX",
"url": "https://git.kernel.org/stable/c/f577508cc8a0adb8b4ebe9480bba7683b6149930"
},
{
"type": "FIX",
"url": "https://git.kernel.org/stable/c/eea6f395ca502c4528314c8112da9b5d65f685eb"
},
{
"type": "FIX",
"url": "https://git.kernel.org/stable/c/b45f721775947a84996deb5c661602254ce25ce6"
}
],
"database_specific": {
"source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
"upstream_modified": "2026-05-12T04:54:46Z"
}
}