HackTesting

CVE-2026-27211

Cloud Hypervisor is a Virtual Machine Monitor for Cloud workloads. Versions 34.0 through 50.0 arevulnerable to arbitrary host file exfiltration (constrained by process privileges) when using virtio-block devices backed by raw images. A malicious guest can overwrite its disk header with a crafted QCOW2 structure pointing to a sensitive host path. Upon the next VM boot or disk scan, the image format auto-detection parses this header and serves the host file's contents to the guest. Guest-initiated VM reboots are sufficient to trigger a disk scan and do not cause the Cloud Hypervisor process to exit. Therefore, a single VM can perform this attack without needing interaction from the management stack. Successful exploitation requires the backing image to be either writable by the guest or sourced from an untrusted origin. Deployments utilizing only trusted, read-only images are not affected. This issue has been fixed in version 50.1. To workaround, enable land lock sandboxing and restrict process privileges and access.

References

https://github.com/cloud-hypervisor/cloud-hypervisor/security/advisories/GHSA-jmr4-g2hv-mjj6
https://github.com/cloud-hypervisor/cloud-hypervisor/commit/081a6ebb5184228ff348601502258f3f72bd8b43
https://github.com/cloud-hypervisor/cloud-hypervisor/commit/509832298b6865365b00bda88722e76e41ce7f41
https://github.com/cloud-hypervisor/cloud-hypervisor/commit/a63315df54e06f6ec867f17b63076c266e2d8648
https://github.com/cloud-hypervisor/cloud-hypervisor/commit/cb495959a8bea1b56e8fc82d15ba527a0e7fcf3c
https://github.com/cloud-hypervisor/cloud-hypervisor/releases/tag/v50.1
https://github.com/cloud-hypervisor/cloud-hypervisor/releases/tag/v51.0