{"api_version":"1","generated_at":"2026-07-15T08:30:49+00:00","cve":"CVE-2026-23005","urls":{"html":"https://cve.report/CVE-2026-23005","api":"https://cve.report/api/cve/CVE-2026-23005.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-23005","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-23005"},"summary":{"title":"x86/fpu: Clear XSTATE_BV[i] in guest XSAVE state whenever XFD[i]=1","description":"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   <TASK>\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   </TASK>\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   <TASK>\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   </TASK>\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---","state":"PUBLISHED","assigner":"Linux","published_at":"2026-01-25 15:15:55","updated_at":"2026-07-14 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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   <TASK>\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   </TASK>\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   <TASK>\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   </TASK>\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---"}],"providerMetadata":{"dateUpdated":"2026-05-11T21:58:09.790Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/b5995c01ba53d84182ecb9492fc4d91cfe8a362d"},{"url":"https://git.kernel.org/stable/c/1e2848bda819af569dfe7ab186223855e092a2cb"},{"url":"https://git.kernel.org/stable/c/f577508cc8a0adb8b4ebe9480bba7683b6149930"},{"url":"https://git.kernel.org/stable/c/eea6f395ca502c4528314c8112da9b5d65f685eb"},{"url":"https://git.kernel.org/stable/c/b45f721775947a84996deb5c661602254ce25ce6"}],"title":"x86/fpu: Clear XSTATE_BV[i] in guest XSAVE state whenever XFD[i]=1","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-23005","datePublished":"2026-01-25T14:36:19.021Z","dateReserved":"2026-01-13T15:37:45.939Z","dateUpdated":"2026-07-14T12:45:44.645Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-01-25 15:15:55","lastModifiedDate":"2026-07-14 13:18:22","problem_types":["NVD-CWE-noinfo"],"metrics":{"cvssMetricV31":[{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","baseScore":5.5,"baseSeverity":"MEDIUM","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":1.8,"impactScore":3.6}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-06-10T20:42:31.188844Z","id":"CVE-2026-23005","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17.1","versionEndExcluding":"6.1.162","matchCriteriaId":"DBDA7572-E110-41C4-9105-D1C8795D891A"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"6.6.122","matchCriteriaId":"8EAAE395-0162-4BAF-9AD5-E9AF3C869C4F"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7","versionEndExcluding":"6.12.67","matchCriteriaId":"7456F614-6AA8-4C08-8229-BA342D4AFBAD"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13","versionEndExcluding":"6.18.7","matchCriteriaId":"99FF3E05-0E7A-44E9-8E47-BF6F1F8EC436"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:5.17:-:*:*:*:*:*:*","matchCriteriaId":"A59F7FD3-F505-48BD-8875-F07A33F42F6C"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.19:rc1:*:*:*:*:*:*","matchCriteriaId":"17B67AA7-40D6-4AFA-8459-F200F3D7CFD1"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.19:rc2:*:*:*:*:*:*","matchCriteriaId":"C47E4CC9-C826-4FA9-B014-7FE3D9B318B2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.19:rc3:*:*:*:*:*:*","matchCriteriaId":"F71D92C0-C023-48BD-B3B6-70B638EEE298"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.19:rc4:*:*:*:*:*:*","matchCriteriaId":"13580667-0A98-40CC-B29F-D12790B91BDB"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.19:rc5:*:*:*:*:*:*","matchCriteriaId":"CAD1FED7-CF48-47BF-AC7D-7B6FA3C065FC"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.19:rc6:*:*:*:*:*:*","matchCriteriaId":"3EF854A1-ABB1-4E93-BE9A-44569EC76C0D"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.19:rc7:*:*:*:*:*:*","matchCriteriaId":"F5DC0CA6-F0AF-4DDF-A882-3DADB9A886A7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.19:rc8:*:*:*:*:*:*","matchCriteriaId":"EB5B7DFC-C36B-45D8-922C-877569FDDF43"}]}]}]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"23005","Ordinal":"1","Title":"x86/fpu: Clear XSTATE_BV[i] in guest XSAVE state whenever XFD[i]","CVE":"CVE-2026-23005","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"23005","Ordinal":"1","NoteData":"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   <TASK>\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   </TASK>\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   <TASK>\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   </TASK>\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---","Type":"Description","Title":"x86/fpu: Clear XSTATE_BV[i] in guest XSAVE state whenever XFD[i]"}]}}}