The ibmasm mouse‑interrupt routine in the Linux kernel reads reader and writer indices directly from hardware MMIO registers and uses them to compute an address for a memory copy. Because the routine performs no bounds check, an attacker can write out‑of‑range values to those registers, causing the kernel to perform an out‑of‑bounds MMIO read through memcpy_fromio. For sufficiently large indices this results in a machine‑check exception that corrupts the state of the kernel and leads to a reboot. This flaw is a classic bounds‑check and integer‑overflow defect (CWE‑1285).

Any Linux kernel that includes the ibmasm module and has not applied the patch that added bounds checks to the queue index handling is potentially vulnerable. Administrators should verify the presence of the fix in their kernel release, but treat all current kernels with ibmasm support as at risk until the patch is confirmed.

With a CVSS score of 5.5 the vulnerability carries a medium severity. The EPSS score is not available, and the flaw is not listed in the CISA KEV catalog, indicating no known large‑scale exploitation. Attackers would need privileged access to the service processor’s MMIO registers to write arbitrary reader or writer values, which is typically outside the scope of unprivileged users. Nonetheless, a compromised or trusted service processor could trigger a denial‑of‑service event and reboot the host.