cbcvebase.
CVE-2025-40026
published 2025-10-28

CVE-2025-40026: In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O When completing…

PriorityP338high7.9CVSS 3.1
AVLACLPRLUINSCCLILAH
EPSS
0.16%
5.5th percentile
In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O When completing emulation of instruction that generated a userspace exit for I/O, don't recheck L1 intercepts as KVM has already finished that phase of instruction execution, i.e. has already committed to allowing L2 to perform I/O. If L1 (or host userspace) modifies the I/O permission bitmaps during the exit to userspace, KVM will treat the access as being intercepted despite already having emulated the I/O access. Pivot on EMULTYPE_NO_DECODE to detect that KVM is completing emulation. Of the three users of EMULTYPE_NO_DECODE, only complete_emulated_io() (the intended "recipient") can reach the code in question. gp_interception()'s use is mutually exclusive with is_guest_mode(), and complete_emulated_insn_gp() unconditionally pairs EMULTYPE_NO_DECODE with EMULTYPE_SKIP. The bad behavior was detected by a syzkaller program that toggles port I/O interception during the userspace I/O exit, ultimately resulting in a WARN on vcpu->arch.pio.count being non-zero due to KVM no completing emulation of the I/O instruction. WARNING: CPU: 23 PID: 1083 at arch/x86/kvm/x86.c:8039 emulator_pio_in_out+0x154/0x170 [kvm] Modules linked in: kvm_intel kvm irqbypass CPU: 23 UID: 1000 PID: 1083 Comm: repro Not tainted 6.16.0-rc5-c1610d2d66b1-next-vm #74 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:emulator_pio_in_out+0x154/0x170 [kvm] PKRU: 55555554 Call Trace: kvm_fast_pio+0xd6/0x1d0 [kvm] vmx_handle_exit+0x149/0x610 [kvm_intel] kvm_arch_vcpu_ioctl_run+0xda8/0x1ac0 [kvm] kvm_vcpu_ioctl+0x244/0x8c0 [kvm] __x64_sys_ioctl+0x8a/0xd0 do_syscall_64+0x5d/0xc60 entry_SYSCALL_64_after_hwframe+0x4b/0x53

Affected

32 ranges· showing 25
VendorProductVersion rangeFixed in
debianlinux< linux 6.1.158-1 (bookworm)linux 6.1.158-1 (bookworm)
debianlinux-6.1< linux 6.1.158-1 (bookworm)linux 6.1.158-1 (bookworm)
linuxlinux
linuxlinux>= 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 < a908eca437789589dd4624da428614c1275064dca908eca437789589dd4624da428614c1275064dc
linuxlinux>= 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 < 00338255bb1f422642fb2798ebe92e93b6e4209b00338255bb1f422642fb2798ebe92e93b6e4209b
linuxlinux>= 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 < e0ce3ed1048a47986d15aef1a98ebda25560d257e0ce3ed1048a47986d15aef1a98ebda25560d257
linuxlinux>= 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 < ba35a5d775799ce5ad60230be97336f2fefd518eba35a5d775799ce5ad60230be97336f2fefd518e
linuxlinux>= 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 < 3d3abf3f7e8b1abb082070a343de82d7efc805233d3abf3f7e8b1abb082070a343de82d7efc80523
linuxlinux>= 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 < e7177c7e32cb806f348387b7f4faafd4a5b32054e7177c7e32cb806f348387b7f4faafd4a5b32054
linuxlinux>= 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 < 3a062a5c55adc5507600b9ae6d911e247e2f1d6e3a062a5c55adc5507600b9ae6d911e247e2f1d6e
linuxlinux>= 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 < 7366830642505683bbe905a2ba5d18d6e4b512b87366830642505683bbe905a2ba5d18d6e4b512b8
linuxlinux>= 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 < e750f85391286a4c8100275516973324b621a269e750f85391286a4c8100275516973324b621a269
linuxlinux_kernel>= 0 < 5.10.247-15.10.247-1
linuxlinux_kernel>= 0 < 6.1.158-16.1.158-1
linuxlinux_kernel>= 0 < 6.12.57-16.12.57-1
linuxlinux_kernel>= 0 < 6.17.6-16.17.6-1
linuxlinux_kernel>= 0 < 5.15.0-170.1805.15.0-170.180
linuxlinux_kernel>= 0 < 6.8.0-106.1066.8.0-106.106
linuxlinux_kernel>= 0 < 6.17.0-7.76.17.0-7.7
linuxlinux_kernel>= 3.0.0 < 5.4.3015.4.301
linuxlinux_kernel>= 5.11.0 < 5.15.1955.15.195
linuxlinux_kernel>= 5.16.0 < 6.1.1576.1.157
linuxlinux_kernel>= 5.5.0 < 5.10.2465.10.246
linuxlinux_kernel>= 6.13.0 < 6.16.126.16.12
linuxlinux_kernel>= 6.17.0 < 6.17.26.17.2

CVSS provenance

nvdv3.17.9HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
osv7.8HIGH
vendor_ubuntu7.8HIGH
vendor_redhat5.5MEDIUM
vendor_msrc3.6LOW
Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.