ITScape / Januscape / Zapscape

What it is

ITScape (CVE-2026-46316) is a KVM guest-to-host escape on arm64, found by Hyunwoo Kim (@v4bel). The repo publishes a PoC and operational guidance following an embargo coordinated through linux-distros@vs.openwall.org. The summary already states the vGIC-ITS race and the in-kernel-KVM location; what the page adds is the affected commit range, the reproduction path, and the precondition/chaining detail below.

Preconditions / Affected

• Only arm64 KVM hosts. The bug is in arch/arm64/kvm/vgic/. Non-arm64 hosts are unaffected.
• Affected range: commit 8201d1028caa (2024-04-25) through 13031fb6b835 (2026-06-05).
• Guest privilege: driving GIC/ITS MMIO requires guest kernel (EL1) privilege. A cloud tenant with root on their own VM already meets this. Without guest root, it must be chained with an LPE such as Dirty Frag.

What to do

Confirm the fix commit 13031fb6b835 is applied to the host kernel — operators directly, tenants via their provider.

To reproduce safely, run under QEMU TCG (triggering is unrelated to QEMU). Download the v7.1-rc6 kernel source (the version just before the patch):

# ./build.sh <linux>/tools/testing/selftests/kvm

Build the kernel image with the bundled kconfig, place the PoC in an initramfs, then:

# ./qemu.sh <kernel-image> <initramfs>

After boot, run the PoC; success creates /ITScape on the host owned by uid=0:

# ./poc
[+] /ITScape created by the host kernel (owner uid=0). verify:  ls -la /ITScape

Caveats

• The released PoC is not a weaponized exploit. It reproduces the full chain on the kvm selftest harness by constructing state host-side. Weaponizing requires porting to a real guest-driven path and tuning addresses, gadget, offsets, and race timing to the target kernel/config. A working real-world exploit exists but is not released.
• Because this is a new vulnerability class, expect variants and follow-ups — but verify any follow-up is genuinely triggerable by guest action alone (no host-side setup) and actually exploitable before treating it as equivalent.

flowchart TD
    A[Guest with EL1 privilege] --> B{Have guest root?}
    B -->|Yes, e.g. own cloud VM| C[Drive GIC/ITS MMIO]
    B -->|No| D[Chain LPE e.g. Dirty Frag] --> C
    C --> E[Trap into in-kernel KVM]
    E --> F[Double-put race in vGIC-ITS]
    F --> G[Host kernel code exec / root]
    P[Patch 13031fb6b835 on host] -. cuts .-> F