CVE-2026-99186
Description
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.
Statement
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | N/A | N/A |
| Attack Vector | Local | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | Low | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | None | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Amplification
An infinite loop will cause unexpected consumption of resources, such as CPU cycles or memory. The software's operation may slow down, or cause a long time to respond.
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