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NVD / CVE Program· CNA Linux

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

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.17% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 00338255bb1f422642fb2798ebe92e93b6e4209b, 3a062a5c55adc5507600b9ae6d911e247e2f1d6e, 3d3abf3f7e8b1abb082070a343de82d7efc80523.

Low priority for now. Upgrade to Linux Linux 00338255bb1f422642fb2798ebe92e93b6e4209b, 3a062a5c55adc5507600b9ae6d911e247e2f1d6e, 3d3abf3f7e8b1abb082070a343de82d7efc80523 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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>

HighCVSS 7.9 · v3.1—No exploit Fix available
Published
Oct 28, 2025
Updated
Oct 19, 2026
EPSS
0.1% · 6th percentile
CWE
—

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
7.9
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 3.0affected
    • 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 and later · before a908eca437789589dd4624da428614c1275064dcaffected · git
    • 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 and later · before 00338255bb1f422642fb2798ebe92e93b6e4209baffected · git
    • 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 and later · before e0ce3ed1048a47986d15aef1a98ebda25560d257affected · git
    • 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 and later · before ba35a5d775799ce5ad60230be97336f2fefd518eaffected · git
    • 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 and later · before 3d3abf3f7e8b1abb082070a343de82d7efc80523affected · git
    • 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 and later · before e7177c7e32cb806f348387b7f4faafd4a5b32054affected · git
    • 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 and later · before 3a062a5c55adc5507600b9ae6d911e247e2f1d6eaffected · git
    • 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 and later · before 7366830642505683bbe905a2ba5d18d6e4b512b8affected · git
    • 8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9 and later · before e750f85391286a4c8100275516973324b621a269affected · git

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8bpftoolbefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernelbefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-abi-stablelistsbefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-corebefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-cross-headersbefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-debugbefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-debug-corebefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-debug-develbefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-debug-modulesbefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-debug-modules-extrabefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-develbefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-docbefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-headersbefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-modulesbefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-modules-extrabefore 4.18.0-553.147.1.el8_104.18.0-553.147.1.el8_10
AlmaLinux:8kernel-rtbefore 4.18.0-553.147.1.rt7.488.el8_104.18.0-553.147.1.rt7.488.el8_10
AlmaLinux:8kernel-rt-corebefore 4.18.0-553.147.1.rt7.488.el8_104.18.0-553.147.1.rt7.488.el8_10
AlmaLinux:8kernel-rt-debugbefore 4.18.0-553.147.1.rt7.488.el8_104.18.0-553.147.1.rt7.488.el8_10
AlmaLinux:8kernel-rt-debug-corebefore 4.18.0-553.147.1.rt7.488.el8_104.18.0-553.147.1.rt7.488.el8_10
AlmaLinux:8kernel-rt-debug-develbefore 4.18.0-553.147.1.rt7.488.el8_104.18.0-553.147.1.rt7.488.el8_10
AlmaLinux:8kernel-rt-debug-modulesbefore 4.18.0-553.147.1.rt7.488.el8_104.18.0-553.147.1.rt7.488.el8_10
AlmaLinux:8kernel-rt-debug-modules-extrabefore 4.18.0-553.147.1.rt7.488.el8_104.18.0-553.147.1.rt7.488.el8_10
AlmaLinux:8kernel-rt-develbefore 4.18.0-553.147.1.rt7.488.el8_104.18.0-553.147.1.rt7.488.el8_10
AlmaLinux:8kernel-rt-modulesbefore 4.18.0-553.147.1.rt7.488.el8_104.18.0-553.147.1.rt7.488.el8_10

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2025-40024Oct 24, 2025 · vhost: Take a reference on the task in struct vhost_task.
    31Monitor
  • ← EarlierCVE-2025-40025Oct 28, 2025 · f2fs: fix to do sanity check on node footer for non inode dnode
    31Monitor
  • Later →CVE-2025-40027Oct 28, 2025 · net/9p: fix double req put in p9_fd_cancelled
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux00338255bb1f422642fb2798ebe92e93b6e4209bVendor (CNA)
Linux Linux3a062a5c55adc5507600b9ae6d911e247e2f1d6eVendor (CNA)
Linux Linux3d3abf3f7e8b1abb082070a343de82d7efc80523Vendor (CNA)
Linux Linux7366830642505683bbe905a2ba5d18d6e4b512b8Vendor (CNA)
Linux Linuxa908eca437789589dd4624da428614c1275064dcVendor (CNA)
Linux Linuxba35a5d775799ce5ad60230be97336f2fefd518eVendor (CNA)
Linux Linuxe0ce3ed1048a47986d15aef1a98ebda25560d257Vendor (CNA)
Linux Linuxe7177c7e32cb806f348387b7f4faafd4a5b32054Vendor (CNA)
Linux Linuxe750f85391286a4c8100275516973324b621a269Vendor (CNA)
almalinux:bpftool4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-abi-stablelists4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-core4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-cross-headers4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-core4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-devel4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules-extra4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-devel4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-doc4.18.0-553.147.1.el8_10 · AlmaLinux:8Package registry (OSV)
debian:linux6.1.158-1 · Debian:12Package registry (OSV)
opensuse:kernel-source6.17.7-1.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:bpftool0:4.18.0-553.147.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:bpftool-debuginfo0:4.18.0-553.147.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel0:4.18.0-553.147.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-abi-stablelists0:4.18.0-553.147.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-core0:4.18.0-553.147.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug0:4.18.0-553.147.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug-core0:4.18.0-553.147.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)

+7

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
high · the service can be disrupted

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality impact
Low
Integrity impact
Low
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (8 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records