CVE-2026-98262
NoneCVSS
—
EPSS
0.2%
Published
Oct 6, 2026
CISA due date
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Cloudanix analysis
Certain hard-drive controllers stop working after a software update, preventing computers from accessing their storage until the problem is fixed in a later update.
- Exploitation
- Local Privilege
- Attacker needs
- Local User
- Complexity
- Theoretical
- Impact
- Denial Of Service
- Component
- OS kernel
- Class
- Other
- Remediation
- Upgrade
- Effort
- Medium
- Patch risk
- Low
What it actually does
The AHCI driver fails to explicitly clear PxCLBU and PxFBU registers when AHCI_HFLAG_32BIT_ONLY is set on 64-bit capable HBAs, causing probe failure and rendering controllers such as JMicron JMB585 unusable.
Why it matters to the business
Affected Linux systems with specific storage controllers experience boot or storage access failures leading to operational downtime; low prevalence and no observed exploitation keep overall risk minimal.
How an attack unfolds
No remote or local attacker exploitation path exists; the flaw is a configuration regression that surfaces automatically during driver initialization on unsupported hardware combinations.
How to fix it
Update to a Linux kernel containing the fix that clears PxCLBU and PxFBU when the 32BIT_ONLY flag is active; no configuration workarounds are documented.
How to confirm the fix worked
Confirm the presence of the commit that adds explicit register clearing for AHCI_HFLAG_32BIT_ONLY controllers and verify successful probe and operation of previously failing JMicron hardware.
Typical attack path
- Kernel loads ahci module and probes HBA
- AHCI_HFLAG_32BIT_ONLY forces 32-bit DMA mask without clearing upper address registers
- Controller enters unusable state immediately after probe
How to detect it
Review kernel boot logs for AHCI probe failures on JMicron JMB582/JMB585 devices; no post-exploitation artifacts exist because the condition prevents normal operation.
What your security team should do
- Apply the corrected kernel version to all affected distributions
- Test storage functionality on hardware known to trigger the flag
- Monitor vendor kernel updates for backports given 17-day publication age
The record
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.
Affected packages
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