{"id":"CVE-2025-40026","revision":"f71f6ab1c5f747f88250f029cd3ca3d0","records":[{"revision":"f71f6ab1c5f747f88250f029cd3ca3d0","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2025-40026","aliases":[],"title":"KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O","description":"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 \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 ","state":0,"publishedAt":"2025-10-28T09:32:33.075+00:00","modifiedAt":"2026-10-15T22:02:36.361+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"arch/x86/kvm/emulate.c\",\n \"arch/x86/kvm/kvm_emulate.h\",\n \"arch/x86/kvm/x86.c\"\n ],\n \"versions\": [\n {\n \"version\": \"8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9\",\n \"lessThan\": \"a908eca437789589dd4624da428614c1275064dc\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9\",\n \"lessThan\": \"00338255bb1f422642fb2798ebe92e93b6e4209b\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9\",\n \"lessThan\": \"e0ce3ed1048a47986d15aef1a98ebda25560d257\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9\",\n \"lessThan\": \"ba35a5d775799ce5ad60230be97336f2fefd518e\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9\",\n \"lessThan\": \"3d3abf3f7e8b1abb082070a343de82d7efc80523\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9\",\n \"lessThan\": \"e7177c7e32cb806f348387b7f4faafd4a5b32054\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9\",\n \"lessThan\": \"3a062a5c55adc5507600b9ae6d911e247e2f1d6e\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9\",\n \"lessThan\": \"7366830642505683bbe905a2ba5d18d6e4b512b8\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9\",\n \"lessThan\": \"e750f85391286a4c8100275516973324b621a269\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"arch/x86/kvm/emulate.c\",\n \"arch/x86/kvm/kvm_emulate.h\",\n \"arch/x86/kvm/x86.c\"\n ],\n \"versions\": [\n {\n \"version\": \"3.0\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"3.0\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.4.301\",\n \"lessThanOrEqual\": \"5.4.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.10.246\",\n \"lessThanOrEqual\": \"5.10.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.15.195\",\n \"lessThanOrEqual\": \"5.15.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.157\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.111\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.52\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.16.12\",\n \"lessThanOrEqual\": \"6.16.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.17.2\",\n \"lessThanOrEqual\": \"6.17.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H","score":7.9,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/a908eca437789589dd4624da428614c1275064dc","https://git.kernel.org/stable/c/00338255bb1f422642fb2798ebe92e93b6e4209b","https://git.kernel.org/stable/c/e0ce3ed1048a47986d15aef1a98ebda25560d257","https://git.kernel.org/stable/c/ba35a5d775799ce5ad60230be97336f2fefd518e","https://git.kernel.org/stable/c/3d3abf3f7e8b1abb082070a343de82d7efc80523","https://git.kernel.org/stable/c/e7177c7e32cb806f348387b7f4faafd4a5b32054","https://git.kernel.org/stable/c/3a062a5c55adc5507600b9ae6d911e247e2f1d6e","https://git.kernel.org/stable/c/7366830642505683bbe905a2ba5d18d6e4b512b8","https://git.kernel.org/stable/c/e750f85391286a4c8100275516973324b621a269"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-40026","license":"CVE Program Terms of Use","key":"cve-program:CVE-2025-40026","identifiers":["CVE-2025-40026"]},"retained":false,"historicalAffected":[]}],"coverage":[]}