CVE-2026-27211: Cloud Hypervisor: Host File Disclosure via Disk Image Header Abuse
Cloud Hypervisor versions from 34.0 before 50.1 can let a malicious guest read host files, with the reach limited by the privileges of the hypervisor process, when virtio-block disks backed by raw images are writable by the guest or come from untrusted sources. The issue is fixed in 50.1. The record shows the CVE is not listed in CISA KEV, and no confirmed exploitation appears in the sources consulted.
Overview
Cloud Hypervisor is a virtual machine monitor for cloud workloads. CVE-2026-27211 describes a host file disclosure issue affecting virtio-block disks backed by raw images. A malicious guest can overwrite its disk header with a crafted QCOW2 structure that points to a sensitive host path, and the image format auto-detection later serves that host file content to the guest.
Impact
- The record states that the disclosure is constrained by the privileges of the Cloud Hypervisor process.
- Guest-initiated VM reboots are enough to trigger a disk scan without the hypervisor process exiting, so a single VM can carry out the scenario without the management stack.
- Exploitation requires the backing image to be writable by the guest or sourced from an untrusted origin.
- The NVD base score is 10 and the GitHub score is 9.1, and the record's severity is critical.
Affected products and versions
- The record lists Cloud Hypervisor versions from 34.0 before 50.1 as affected. The description names the range 34.0 through 50.0.
- Deployments using only trusted, read-only images are described as not affected.
- The issue is fixed in 50.1, as stated in the release notes.
Exploitation status
The record shows that the CVE is not listed in the CISA Known Exploited Vulnerabilities catalog. No confirmed exploitation appears in the sources consulted. The SSVC data in the record marks exploitation as none and automatable as no. The EPSS probability is 0.00675 with a percentile of 0.51664.
Remediation and mitigation
- Upgrade Cloud Hypervisor to 50.1 or later, following the security advisory.
- Until the upgrade is done, enable landlock sandboxing and restrict the process privileges and file access, as the advisory describes as a workaround.
- Treat guest-writable disk images as untrusted, and prefer read-only images from trusted sources.
- Review the patch commits linked from the NVD record for technical details of the change.
Detection guidance
- Inventory VMs that use virtio-block with raw images, and note which disks are writable by the guest or come from external sources.
- Monitor for unexpected changes to disk image headers, especially images whose format metadata no longer matches the expected raw format.
- Watch for repeated guest reboots on sensitive VMs, since these trigger disk scans.
- Audit host file access logs of the hypervisor process where they are available.
Limitations of the available information
- The record does not include a detailed analysis of the patch behavior, so the patch commits are cited but not analyzed here.
- The CWE identifier is CWE-73, but the record gives no name for it.
- The specific host files that could be exposed depend on process privileges, which the record does not describe.
- The record does not state whether other release lines received backports.
Frequently asked questions
Is this vulnerability being actively exploited?
The record shows the CVE is not listed in CISA KEV, and no confirmed exploitation appears in the sources consulted.
Which version fixes the issue?
The release notes and the record indicate the issue is fixed in 50.1.
Does my deployment need to act?
If you run Cloud Hypervisor from 34.0 before 50.1 with guest-writable or untrusted raw disk images, prioritize upgrading to 50.1 and restricting process privileges.
This analysis was drafted with AI assistance from verified source data and automatically checked against it.