Ubuntu USN-8664-1 Advisory: Linux Kernel AMD Zen 2 Cache Isolation Flaw Allows Privilege Escalation

Vulnerability Overview Vulnerability ID: USN-8664-1 Publication Date: August 20, 2026 Affected System: Linux kernel (NVIDIA BaseOS) Vulnerability Description: A vulnerability has been identified in which certain AMD Zen 2 processors do not properly isolate shared resources in the operating cache. A local attacker could exploit this issue to execute corrupted instructions at a higher privilege level, resulting in a privilege escalation. Scope of Impact Affected Subsystems: - x86 platform drivers - Cryptographic API - PSP security protocol - ARM32 architecture - ARM64 architecture - MIPS architecture - PowerPC architecture - RISC-V architecture - s390 architecture - User Mode Linux (UML) - x86 architecture - Block layer subsystem - Intel NPU driver - Compute acceleration framework - ACPI drivers - Accessibility Remediation Update Instructions: - A system restart is required after a standard system update to complete all necessary changes. - Due to unavoidable ABI changes, the kernel update has been assigned a new version number, requiring all third-party kernel modules to be recompiled and reinstalled. - This action is performed automatically during a standard system upgrade unless the standard kernel meta-packages (such as , , , ) have been manually removed. Fixed Versions: - Ubuntu 26.04 LTS: - – 7.0.0-2016.16 - – 7.0.0-2016.16 - – 7.0.0-2016.16 - – 7.0.0-2016.16 - – 7.0.0-2016.16 - – 7.0.0-2016.16 - – 7.0.0-2016.16 - – 7.0.0-2016.16 References CVE-2026-64528 CVE-2026-64527 CVE-2026-64526 CVE-2026-64525 CVE-2026-64524 CVE-2026-64523 CVE-2026-64522 CVE-2026-64521 CVE-2026-64519 CVE-2026-64518 Related Notices USN-8663-1 USN-8662-1 USN-8661-1 USN-8660-1 USN-8658-1 USN-8656-1 USN-8646-1 USN-8645-1 USN-8644-1 USN-8644-2 Reducing Security Exposure Ubuntu Pro provides ten years of security coverage covering more than 25,000 packages in the Main and Universe repositories, free for use on up to five machines. Additional Information Contact Team: For any additional questions, please contact the team members.

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Ubuntu USN-8664-1 Advisory: Linux Kernel AMD Zen 2 Cache Isolation Flaw Allows Privilege Escalation

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