CVE-2026-90315

Lockdown bypass via unchecked legacy PCI access

Published Sep 17, 2026 · Updated Sep 17, 2026

Lockdown bypass in Linux 5.4 PCI sysfs allows local users with root privileges to write I/O ports and map memory despite lockdown. The pci_write_legacy_io(), pci_mmap_legacy_mem(), and pci_mmap_legacy_io() handlers omit security_locked_down(LOCKDOWN_PCI_ACCESS), accepting legacy access requests without enforcing the restriction. Exposure requires HAVE_PCI_LEGACY support, including Alpha and PowerPC; the bypass restores hardware access that lockdown prohibits to protect kernel code.

CVSS severity6.7
Medium
EPSS probability0.21%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Lockdown bypass in Linux 5.4 PCI sysfs allows local users with root privileges to write I/O ports and map memory despite lockdown. The pci_write_legacy_io(), pci_mmap_legacy_mem(), and pci_mmap_legacy_io() handlers omit security_locked_down(LOCKDOWN_PCI_ACCESS), accepting legacy access requests without enforcing the restriction. Exposure requires HAVE_PCI_LEGACY support, including Alpha and PowerPC; the bypass restores hardware access that lockdown prohibits to protect kernel code.

The record

CVE
CVE-2026-90315
Published
Sep 17, 2026
Updated
Sep 17, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Sep 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.4
  2. Affected versionversion=eb627e17727ebeede70697ae1798688b0d328b54 <747b9bbbbdfdee51aee2456388f9b94b5086de4d
  3. Affected versionversion=eb627e17727ebeede70697ae1798688b0d328b54 <cd07aef510ac6a2873e01f9ddddc5492490b0067

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linuxversion=5.4; version=eb627e17727ebeede70697ae1798688b0d328b54 <747b9bbbbdfdee51aee2456388f9b94b5086de4d; version=eb627e17727ebeede70697ae1798688b0d328b54 <cd07aef510ac6a2873e01f9ddddc5492490b0067

Published CVSS scores

6.7Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
6.7SUSECVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

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No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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