{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2025-40026", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.152Z", "datePublished": "2025-10-28T09:32:33.075Z", "dateUpdated": "2026-05-11T21:41:03.028Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-05-11T21:41:03.028Z"}, "descriptions": [{"lang": "en", "value": "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": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/x86/kvm/emulate.c", "arch/x86/kvm/kvm_emulate.h", "arch/x86/kvm/x86.c"], "versions": [{"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "a908eca437789589dd4624da428614c1275064dc", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "00338255bb1f422642fb2798ebe92e93b6e4209b", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "e0ce3ed1048a47986d15aef1a98ebda25560d257", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "ba35a5d775799ce5ad60230be97336f2fefd518e", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "3d3abf3f7e8b1abb082070a343de82d7efc80523", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "e7177c7e32cb806f348387b7f4faafd4a5b32054", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "3a062a5c55adc5507600b9ae6d911e247e2f1d6e", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "7366830642505683bbe905a2ba5d18d6e4b512b8", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "e750f85391286a4c8100275516973324b621a269", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/x86/kvm/emulate.c", "arch/x86/kvm/kvm_emulate.h", "arch/x86/kvm/x86.c"], "versions": [{"version": "3.0", "status": "affected"}, {"version": "0", "lessThan": "3.0", "status": "unaffected", "versionType": "semver"}, {"version": "5.4.301", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.10.246", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.15.195", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.157", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.111", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.52", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.16.12", "lessThanOrEqual": "6.16.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.17.2", "lessThanOrEqual": "6.17.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "5.4.301"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "5.10.246"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "5.15.195"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.1.157"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.6.111"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.12.52"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.16.12"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.17.2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.18"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/a908eca437789589dd4624da428614c1275064dc"}, {"url": "https://git.kernel.org/stable/c/00338255bb1f422642fb2798ebe92e93b6e4209b"}, {"url": "https://git.kernel.org/stable/c/e0ce3ed1048a47986d15aef1a98ebda25560d257"}, {"url": "https://git.kernel.org/stable/c/ba35a5d775799ce5ad60230be97336f2fefd518e"}, {"url": "https://git.kernel.org/stable/c/3d3abf3f7e8b1abb082070a343de82d7efc80523"}, {"url": "https://git.kernel.org/stable/c/e7177c7e32cb806f348387b7f4faafd4a5b32054"}, {"url": "https://git.kernel.org/stable/c/3a062a5c55adc5507600b9ae6d911e247e2f1d6e"}, {"url": "https://git.kernel.org/stable/c/7366830642505683bbe905a2ba5d18d6e4b512b8"}, {"url": "https://git.kernel.org/stable/c/e750f85391286a4c8100275516973324b621a269"}], "title": "KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "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>"}], "id": "CVE-2025-40026", "lastModified": "2026-04-15T00:35:42.020", "metrics": {}, "published": "2025-10-28T10:15:42.167", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/00338255bb1f422642fb2798ebe92e93b6e4209b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/3a062a5c55adc5507600b9ae6d911e247e2f1d6e"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/3d3abf3f7e8b1abb082070a343de82d7efc80523"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/7366830642505683bbe905a2ba5d18d6e4b512b8"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/a908eca437789589dd4624da428614c1275064dc"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/ba35a5d775799ce5ad60230be97336f2fefd518e"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/e0ce3ed1048a47986d15aef1a98ebda25560d257"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/e7177c7e32cb806f348387b7f4faafd4a5b32054"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/e750f85391286a4c8100275516973324b621a269"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Deferred"}

{"bugzilla": {"description": "kernel: KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O", "id": "2406712", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2406712"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "details": ["No description is available for this CVE."], "name": "CVE-2025-40026", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-10-28T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-40026\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-40026\nhttps://lore.kernel.org/linux-cve-announce/2025102841-CVE-2025-40026-760b@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-10-29T10:58:46.658106+00:00", "updated": "2025-10-29T10:58:46.658131+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}