A flaw in the Linux AHCI driver causes the kernel to crash when the host controller reports a number of ports that do not fit within the memory‑mapped I/O (BAR) region. The driver calculates the required size as 0x100 for global registers plus 0x80 bytes per advertised port. If the controller’s BAR is smaller than this requirement, the driver accesses memory beyond the valid region, resulting in a kernel panic. The incident is triggered when a BIOS reports an incorrect CAP.NP field, such as 0xFFFFFFFF, which can make the driver believe the controller has 32 ports while only a smaller number are physically present.

The vulnerability affects Linux kernel systems that load the AHCI driver on hardware where the BIOS may report an incorrect Number of Ports. All kernel versions prior to the patch are potentially susceptible, but the data does not list specific kernel releases. The issue is hardware‑specific, requiring an AHCI controller and a BIOS that can supply a bogus port count. Any system using such hardware with the AHCI driver enabled is at risk.

With a CVSS score of 5.5 the severity is moderate. The EPSS score is under 1% and the vulnerability is not in CISA KEV, indicating no known exploits. Because the trigger relies on a BIOS‑reported value, an attacker would likely need local or physical access to modify firmware settings, making remote exploitation unlikely. Nonetheless, local attackers could force a denial of service by manipulating BIOS or by physically changing the controller, causing repeated kernel panics. The patch prevents memory accesses beyond the BAR boundary and reports a clear error instead of crashing.