CVE-2026-46174: x86/CPU/AMD: Prevent improper isolation of shared resources in Zen2's op cache

Synopsis

This is a CPU microarchitecture isolation flaw in the Linux kernel affecting AMD Zen2 processors. A local attacker with a low-privilege account can exploit improper resource sharing in the Zen2 op cache (the CPU's micro-op decode cache) to corrupt instructions being executed by other processes or virtual machines on the same physical host. Successful exploitation allows an attacker to read sensitive data, tamper with execution, or crash affected workloads running on the same CPU. Patched-image rebuilds at the fix commits are available on HarborGuard for environments running an affected kernel version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityNot required

  The attacker needs an existing shell or process on the host; no network access to the target is required.

• AuthenticationRequired

  Any low-privilege local account is sufficient; no administrative or elevated credentials are needed.

• Victim interactionNot required

  No action by another user or victim is needed; the attacker can exploit the flaw entirely on their own.

• Attack complexityDetail

  Attack complexity is low, meaning the exploit is reliable and does not depend on race conditions, special memory layouts, or other variable environmental factors.

Blast Radius

• Reads protected memory from other processes or guest VMs sharing the same physical CPU core, including secrets, session tokens, or cryptographic key material.
• Corrupts instructions being decoded by co-located workloads, enabling tampering with their execution flow or persisted state.
• Crashes affected processes or guest VMs through instruction corruption, causing service disruption on the host.
• Because the scope is changed (S:C in the CVSS vector), impact extends beyond the attacker's own process boundary to other security contexts on the same physical host.