CVE-2026-27211

Critical

Published: 21 February 2026

Published

21 February 2026

Modified

24 February 2026

KEV Added

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Patch

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CVSS Score 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

EPSS Score 0.0006 17.1th percentile

Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-27211 is a critical-severity External Control of File Name or Path (CWE-73) vulnerability in Cloudhypervisor Cloud Hypervisor. Its CVSS base score is 10.0 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Escape to Host (T1611); ranked at the 17.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 AC-6 (Least Privilege) and SC-4 (Information in Shared System Resources).

Threat & Defense at a Glance

What attackers do: exploitation maps to Escape to Host (T1611) and 2 other techniques. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

Timely patching to Cloud Hypervisor version 50.1 or later directly remediates the improper image format auto-detection that enables host file exfiltration.

AC-6 Least Privilege good match

prevent

Restricting Cloud Hypervisor process privileges, as recommended in the workaround, prevents access to sensitive host files even if a crafted QCOW2 header is parsed.

SC-4 Information in Shared System Resources good match

prevent

Prevents unauthorized information transfer via shared virtio-block backing images by enforcing controls that block guest manipulation from exposing host files.

MITRE ATT&CK Enterprise TechniquesAI

T1611 Escape to Host Privilege Escalation

Adversaries may break out of a container or virtualized environment to gain access to the underlying host.

attack.mitre.org →

T1005 Data from Local System Collection

Adversaries may search local system sources, such as file systems, configuration files, local databases, virtual machine files, or process memory, to find files of interest and sensitive data prior to Exfiltration.

attack.mitre.org →

T1068 Exploitation for Privilege Escalation Privilege Escalation

Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.

attack.mitre.org →

Why these techniques?

Vuln enables guest-to-host escape (T1611) via crafted disk header for arbitrary host file read/exfil (T1005); directly supports priv esc from guest context (T1068).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

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.

Deeper analysisAI

Cloud Hypervisor, a Virtual Machine Monitor for cloud workloads, contains a vulnerability in versions 34.0 through 50.0 that enables arbitrary host file exfiltration when using virtio-block devices backed by raw images. The issue, tracked as CVE-2026-27211 and published on 2026-02-21, stems from improper handling of image format auto-detection. A malicious guest can overwrite its disk header with a crafted QCOW2 structure that points to a sensitive host path. Upon the next VM boot or disk scan, this header is parsed, causing the contents of the specified host file to be served to the guest. The vulnerability is rated CVSS 10.0 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N) and maps to CWE-73 (External Control of File Name or Path).

A malicious guest can exploit this without needing interaction from the management stack, as guest-initiated VM reboots are sufficient to trigger a disk scan and do not cause the Cloud Hypervisor process to exit. Exploitation requires the backing image to be writable by the guest or sourced from an untrusted origin; deployments using only trusted, read-only images are unaffected. Successful attacks allow exfiltration of host files, constrained by the privileges of the Cloud Hypervisor process, potentially exposing sensitive data across scope from network-accessible guests.

The vulnerability has been addressed in Cloud Hypervisor version 50.1, as detailed in the project's GitHub release and related commit fixes. As a workaround, enable Landlock sandboxing and restrict process privileges and access to mitigate risks until patching is feasible.