An out‑of‑bounds write occurs when the Linux kernel’s s390 boot code parses IPL parameters during the boot process. If the command line consumes all but the last byte of the COMMAND_LINE_SIZE buffer, the helper that converts the IPL parameter receives a size of zero and writes the result one byte beyond the end of the early_command_line storage area. This write can corrupt adjacent kernel memory, causing a system crash or other unintended behaviour. No evidence is given that an attacker could achieve arbitrary code execution, so the impact is limited to memory corruption and possible denial of service.

Linux kernels compiled for the s390 architecture are affected. The advisory lists only the vendor Linux:Linux, and no specific kernel release numbers are provided, so any kernel containing the vulnerable s390/boot path could be impacted.

The CVSS score is 7.0, and the EPSS score is reported as <1%, indicating a very low probability of exploitation at this time. The vulnerability is not catalogued in CISA KEV. The attack vector is boot‑time manipulation of IPL parameters; it requires access that can modify the early boot command line, such as physical access to the boot loader or the ability to modify boot media. An attacker could thus trigger the out‑of‑bounds write with a crafted parameter during system start, leading to kernel memory corruption and the risk of a crash. The overall risk is modest because exploitation needs specialized boot‑level access and the likelihood of exploitation is low.