Raw vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XSummary
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 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Data from Local System (T1005); ranked at the 40th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) and AC-3 (Access Enforcement) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
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.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-7729
Vulnerability Data
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…
more
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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
—
—
—
V5.3.2
Mitigating Controls (NIST 800-53 r5) AI
Input validation directly rejects or sanitizes untrusted path strings before they reach filesystem operations.
Enforces authorization checks on the actual resource accessed, blocking unauthorized files even when a malicious path is supplied.
Least-privilege limits the set of files or directories any subject can affect, shrinking the blast radius of a path-control flaw.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect path-traversal issues but does not itself implement preventive controls.
Secure development lifecycle mandates input validation and path-handling controls that directly prevent external file/path manipulation.
Application security requirements explicitly call for controls against untrusted input influencing file operations.
Secure architecture principles discourage unsafe path construction but do not prescribe concrete file-name controls.
Secure coding standards require canonicalization, allow-listing, and bounds checks on file paths, directly eliminating CWE-73.
Information access restriction limits which files can be reached, indirectly reducing impact of path manipulation.