An EPYC escape: Case-study of a KVM breakout
Summary: Google Project Zero's Felix Wilhelm published the first public writeup of a KVM guest-to-host escape that does not rely on user space components such as QEMU, exploiting CVE-2021-29657 in KVM's AMD-specific nested virtualization code. The bug affects kernel versions v5.10-rc1 to v5.12-rc6, was patched at the end of March 2021, and is a double-fetch flaw where a guest with multiple CPU cores can modify VMCB fields after nested_vmcb_checks verifies them but before load_nested_vmcb_control copies them.
Key Takeaway: KVM is the de-facto hypervisor for Linux-based cloud outside Azure, and this bug became exploitable only in v5.10 and was found roughly five months later - a window that shows how briefly a hypervisor boundary can sit open before anyone notices.
Read the original at Google Project Zero ↗
- Topics
- Supply Chain & AppSec
- Mentions
- CVE-2021-29657
- Related
- Kitesurf is now open source Cyber Risks · Nov 13, 2026Trained to betray: How post-training supply chain attacks hijack coding agents Cyber Risks · Nov 12, 2026ZDI-26-913: (0Day) Meta fairseq load_audio_path Code Injection Remote Code Execution Vulnerability Cyber Risks · Nov 11, 2026