CVE-2026-99186

A flaw was found in the Linux kernel's x86 instruction evaluation component. A local user can exploit this vulnerability to cause a Denial of Service (DoS) by executing instructions with segment register overrides that trigger an infinite loop during instruction decoding. This condition traps the processor core in kernel mode, tying up CPU resources until the system is rebooted. Additionally, improper segment prefix processing may cause emulated instruction results to be written to unintended memory locations.

This vulnerability is rated as Moderate impact because an authenticated local unprivileged attacker can induce an infinite loop within the kernel to exhaust system CPU resources, but cannot directly escalate privileges or breach confidentiality. Exploitation occurs during user-space instruction emulation on x86 architectures when processing specific segment prefixes, resulting in core hangs that persist until the system is restarted. Because the attack vector is restricted to local access and does not allow remote exploitation, the overall operational risk remains bounded.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.