Google Cloud has warned customers that three CPU side-channel flaws in AMD Turin processors could allow data leakage between processes inside virtual machines. The affected machine series include C4D, N4D, H4D, Z4D, and G4, along with bare-metal instances of C4D and Z4D.
Turin is the codename for fifth-generation AMD EPYC processors based on the Zen 5 architecture. All three vulnerabilities are classified as Transient Scheduler Attacks (TSA). Two of them, TSA-SQ (CVE-2024-36350) and TSA-L1 (CVE-2024-36357), were previously disclosed for earlier EPYC generations, while the third flaw, CVE-2026-0004 (also called TSA-Fill by the Xen Project), is new.
The flaws may allow an attacker with code execution on the same processor core to infer sensitive data from other processes or the kernel via the L1 data cache. Google Cloud has already deployed mitigations to prevent cross-VM and VM-to-host attacks. The company rates the issue as Medium severity.
Recommended Actions for Customers
- VMs: Install the guest OS vendor patch when available, then stop and start the instance after the CPU information update is applied.
- Bare metal: Apply platform firmware and OS updates from respective vendors for C4D and Z4D instances.
- GKE: Upgrade nodes once updated images for Turin-based bare metal become available.
- Cloud Run: No action required.
AMD states that both firmware and operating system updates are necessary for full mitigation on Zen 5 systems. The Xen Project has published hypervisor patches, and microcode updates have been available in linux-firmware since September 23. As of now, none of the CVEs appear in CISA’s KEV catalog, and no in-the-wild exploitation has been reported.
