CVE-2026-100839
Received Received - Intake

AML Injection in Contrast Kubernetes Runtime

Publication date: 2026-09-27

Last updated on: 2026-09-27

Assigner: VulnCheck

Description
Contrast is a confidential-computing runtime for Kubernetes. In versions before 1.18.0, the guest kernel's ACPI/AML handling is vulnerable to an AML injection attack ("BadAML"). ACPI tables containing AML bytecode are passed from the untrusted host (QEMU) to the guest firmware (OVMF) and on to the Linux kernel, whose AML interpreter executes them. An attacker controlling the host — an assumed adversary in Contrast's threat model — can craft a table with malicious, Turing-complete AML bytecode that the guest kernel interprets with access to the full guest memory, including private pages, resulting in arbitrary code execution and disclosure or modification of confidential guest data. The issue affects the AMD SEV-SNP platforms Metal-QEMU-SNP and Metal-QEMU-SNP-GPU; Metal-QEMU-TDX is not affected because ACPI table contents are measured into RTMR 0 by OVMF on Intel TDX. Version v1.18.0 mitigates the attack by sandboxing the kernel AML interpreter so that it cannot read or write private memory pages. This weakness is not specific to Contrast but is generic to Confidential Computing setups that expose the ACPI interface to the host.

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Meta Information

Published
2026-09-27
Last Modified
2026-09-27
Generated
2026-09-27
AI Q&A
2026-09-27
EPSS Evaluated
N/A
NVD
CVE-2026-100839
EUVD
EUVD-2026-87849

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
contrast contrast to 1.18.0 (exc)
qemu qemu *
edgelesssys contrast *

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-94 The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.

Attack-Flow Graph

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Executive Summary

This vulnerability, named BadAML, is an AML (ACPI Machine Language) injection attack affecting Contrast versions before 1.18.0. It allows an attacker controlling the host (QEMU) to inject malicious AML bytecode into ACPI tables passed to the guest firmware (OVMF) and then to the Linux kernel. The AML interpreter in the kernel executes this code with full access to guest memory, including private pages, enabling arbitrary code execution and potential data disclosure or modification.

Detection Guidance

Detecting this vulnerability requires checking the Contrast version and platform configuration. For Contrast, verify if the installed version is before 1.18.0. On AMD SEV-SNP platforms (Metal-QEMU-SNP, Metal-QEMU-SNP-GPU), inspect ACPI table handling in QEMU and OVMF logs for suspicious AML bytecode. Use commands like 'contrast version' to check the version and 'dmesg | grep AML' to search for AML-related kernel messages.

Impact Analysis

An attacker exploiting this flaw could execute arbitrary code within a confidential virtual machine, access or modify sensitive data, and bypass security controls. This could lead to data breaches, unauthorized system access, or compromise of confidential information stored in the guest environment.

Compliance Impact

This vulnerability could lead to unauthorized access or disclosure of personal or sensitive data, violating compliance requirements under GDPR, HIPAA, and other regulations. Organizations using affected Contrast versions may face legal penalties, reputational damage, and loss of trust due to potential data breaches.

Mitigation Strategies

Upgrade Contrast to version 1.18.0 or later to apply the AML interpreter sandboxing fix. For AMD SEV-SNP platforms, ensure ACPI table contents are measured into RTMR 0 if using Intel TDX. Isolate untrusted hosts and restrict QEMU access to ACPI tables. Monitor for unusual guest kernel behavior or memory access patterns.

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