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这是首次公开的、同时影响 Intel 和 AMD 的客户机到宿主机 KVM 利用技术，曾作为 0-day 用于 Google kvmCTF 竞赛，且潜伏期长达 16 年，影响主要公有云。

适合谁使用

云安全工程师
KVM/虚拟化开发者
公有云租户（如 GCP、AWS）
Linux 发行版维护者

典型使用场景

测试多租户环境中 KVM 宿主机隔离性
展示限制嵌套虚拟化的必要性
评估云服务提供商的漏洞影响范围
理解长期存在的内核内存安全缺陷

项目优势

首个跨架构（Intel/AMD）的 KVM 逃逸利用
在 Google kvmCTF 中被确认为 0-day
可实现宿主机完全控制（RCE）而非仅拒绝服务
潜伏约 16 年，体现深层内核缺陷的持久性

使用前须知

需要客户机 root 权限加载 PoC 模块
需要宿主机启用嵌套虚拟化
完整逃逸利用尚未公开，仅提供拒绝服务 PoC

README 快速开始

Januscape: Guest-to-Host Escape in KVM/x86

Abstract

This document describes the Januscape (CVE-2026-53359) vulnerability discovered and reported by Hyunwoo Kim (@v4bel). It is a KVM escape vulnerability that lets a guest escape to the host in a KVM/x86 environment. To the best of public knowledge, this is the first guest-to-host exploit research triggerable on both Intel and AMD rather than being limited to a single architecture.

Januscape is a use-after-free vulnerability in the shadow MMU emulation of KVM/x86. It can trigger the bug with guest-side actions alone to corrupt the host kernel's shadow page, and it can threaten the guest-host isolation of KVM/x86 hosts that accept untrusted guests and expose nested virtualization, particularly multi-tenant x86 public clouds (GCP, AWS, etc.).

In fact, Januscape was successfully used as a 0-day exploit in Google kvmCTF.

For the detailed technical information, see here.

[!NOTE] After reporting this vulnerability to linux-distros@vs.openwall.org, the agreed embargo has ended, so the exploit is posted to oss-security and this Januscape document is published. For the disclosure timeline, see the technical detail document.

PoC Structure

Running the PoC inside a guest VM can trigger a host kernel panic. A full escape exploit that works in a controlled environment also exists, but it is not released at this time and is planned to be released in the very distant future.

On distributions like RHEL, /dev/kvm is world-writable (0666), so an unprivileged user could also turn this vulnerability into a reliable LPE to root. That said, doing so would be like paying gold for garbage, so I won't bother covering it.

PoC Usage

Inside the guest VM, install the headers and build the module.

# sudo apt-get install -y build-essential linux-headers-$(uname -r)
# make

Load the module inside the guest. KVM holds the raw VMX/SVM state, so unload it first. Load with no argument on Intel, and with amd=1 on AMD.

[Intel]
# sudo rmmod kvm_intel; sudo insmod poc.ko

[AMD]
# sudo rmmod kvm_amd; sudo insmod poc.ko amd=1

The race starts, and within seconds to minutes the host KVM panics.

[*] poc step 4/4: race live -- host DoS triggering
...
kern

Januscape