CVE-2026-100839 Details

A vulnerability exists in Contrast, a confidential-computing runtime for Kubernetes, in versions prior to 1.18.0. The issue arises from the guest kernel's handling of ACPI/AML, which is susceptible to an AML injection attack known as 'BadAML'. In this vulnerability, ACPI tables containing AML bytecode are transmitted from the untrusted host (QEMU) to the guest firmware (OVMF) and subsequently to the Linux kernel. The kernel's AML interpreter executes this bytecode, which is Turing-complete and has access to the entire guest memory, including private pages. This exploitation leads to arbitrary code execution and the unauthorized disclosure or modification of confidential guest data. The vulnerability is present on AMD SEV-SNP platforms, specifically Metal-QEMU-SNP and Metal-QEMU-SNP-GPU. However, Metal-QEMU-TDX is not affected, as OVMF measures ACPI table contents into RTMR 0 on Intel TDX, preventing such attacks. The vulnerability allows an attacker controlling the host to craft a table with malicious AML bytecode that the guest kernel executes, exploiting the full access to guest memory for unauthorized actions.

Users should upgrade to Contrast version 1.18.0 or later, which addresses this vulnerability by sandboxing the kernel AML interpreter to prevent access to private memory pages. Instructions for updating can be found in the Contrast documentation.