CVE-2026-100839: AML Injection Vulnerability in Contrast Runtime

Contrast is a confidential-computing runtime designed for Kubernetes environments. A vulnerability identified as CVE-2026-100839 exists in versions prior to 1.18.0, stemming from how the guest kernel handles ACPI/AML (Advanced Configuration and Power Interface / ACPI Machine Language) bytecode. In this threat model, an adversary controlling the host (e.g., via QEMU) can craft malicious ACPI tables containing Turing-complete AML bytecode.

This bytecode is passed to the guest firmware (OVMF) and subsequently executed by the guest Linux kernel's AML interpreter. Because the interpreter lacks sufficient isolation in older versions, it can access the full guest memory space, including private memory pages. This allows the host adversary to perform unauthorized reads or modifications of sensitive guest data and achieve arbitrary code execution within the guest. This issue specifically affects AMD SEV-SNP platforms, including Metal-QEMU-SNP and Metal-QEMU-SNP-GPU, whereas Intel TDX environments are protected by measurements in RTMR 0. Version 1.18.0 addresses this by sandboxing the AML interpreter.

Impact

Successful exploitation allows a malicious host to break the confidentiality and integrity guarantees of the confidential-computing runtime. An attacker can gain arbitrary code execution inside the guest container or virtual machine, facilitating the exfiltration or modification of private memory contents. This impacts users running sensitive workloads on AMD SEV-SNP platforms using the affected versions of the Contrast runtime.

Recommendation

Prioritize the upgrade of all Contrast runtime instances running on AMD SEV-SNP platforms to version 1.18.0 or later to ensure the kernel AML interpreter is properly sandboxed. Given the fundamental nature of this vulnerability in ACPI handling, monitor for unexpected kernel-level activity originating from the ACPI subsystem, although detection at the guest level may be difficult due to the nature of the exploit.