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CVE-2025-40026— KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于完成用户空间IO时未重新检查L1拦截，可能导致错误的IO访问处理。

CVSS 7.9 · High EPSS 0.17% · P6

Affected Version Matrix 20

VendorProduct Version RangeStatus
Linux Linux 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9< a908eca437789589dd4624da428614c1275064dc affected
8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9< 00338255bb1f422642fb2798ebe92e93b6e4209b affected
8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9< e0ce3ed1048a47986d15aef1a98ebda25560d257 affected
8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9< ba35a5d775799ce5ad60230be97336f2fefd518e affected
8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9< 3d3abf3f7e8b1abb082070a343de82d7efc80523 affected
8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9< e7177c7e32cb806f348387b7f4faafd4a5b32054 affected
8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9< 3a062a5c55adc5507600b9ae6d911e247e2f1d6e affected
8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9< 7366830642505683bbe905a2ba5d18d6e4b512b8 affected
… +12 more rows
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I. Basic Information for CVE-2025-40026

Vulnerability Information
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Vulnerability Title
KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O
Source: CVE Program / CVE List V5
Vulnerability Description
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: <TASK> 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 </TASK>
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于完成用户空间IO时未重新检查L1拦截，可能导致错误的IO访问处理。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 ~ a908eca437789589dd4624da428614c1275064dc -
Linux Linux 3.0 -

II. Public POCs for CVE-2025-40026

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III. Intelligence Information for CVE-2025-40026

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Patches & Fixes for CVE-2025-40026 (9)

Same Patch Batch · Linux · 2025-10-28 · 58 CVEs total

CVE-2025-40074 9.8 CRITICAL ipv4: start using dst_dev_rcu()
CVE-2025-40043 8.8 HIGH net: nfc: nci: Add parameter validation for packet data
CVE-2025-40039 8.8 HIGH ksmbd: Fix race condition in RPC handle list access
CVE-2025-40058 8.8 HIGH iommu/vt-d: Disallow dirty tracking if incoherent page walk
CVE-2025-40046 8.6 HIGH io_uring/zcrx: fix overshooting recv limit
CVE-2025-40068 8.4 HIGH fs: ntfs3: Fix integer overflow in run_unpack()
CVE-2025-40075 8.1 HIGH tcp_metrics: use dst_dev_net_rcu()
CVE-2025-40025 7.8 HIGH f2fs: fix to do sanity check on node footer for non inode dnode
CVE-2025-40027 7.8 HIGH net/9p: fix double req put in p9_fd_cancelled
CVE-2025-40028 7.8 HIGH binder: fix double-free in dbitmap
CVE-2025-40045 7.8 HIGH ASoC: codecs: wcd937x: set the comp soundwire port correctly
CVE-2025-40047 7.8 HIGH io_uring/waitid: always prune wait queue entry in io_waitid_wait()
CVE-2025-40051 7.8 HIGH vhost: vringh: Modify the return value check
CVE-2025-40054 7.8 HIGH f2fs: fix UAF issue in f2fs_merge_page_bio()
CVE-2025-40061 7.8 HIGH RDMA/rxe: Fix race in do_task() when draining
CVE-2025-40064 7.8 HIGH smc: Fix use-after-free in __pnet_find_base_ndev().
CVE-2025-40067 7.8 HIGH fs/ntfs3: reject index allocation if $BITMAP is empty but blocks exist
CVE-2025-40069 7.8 HIGH drm/msm: Fix obj leak in VM_BIND error path
CVE-2025-40079 7.8 HIGH riscv, bpf: Sign extend struct ops return values properly
CVE-2025-40081 7.8 HIGH perf: arm_spe: Prevent overflow in PERF_IDX2OFF()

Showing top 20 of 58 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-40026

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