External risk intelligence

Incus RCE via metadata.yaml symlink vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.9)

CVE-2026-63343

Incus is a system container and virtual machine manager typically deployed in internal, administrative, or restricted environments. While it may be reachable over a network, it is generally not exposed directly to the public internet, and access is typically limited to authenticated administrators or developers managing infrastructure.

Halo Surface Signal: 2 out of 5 — less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This vulnerability impacts Incus, a system for managing containers and virtual machines, allowing authenticated users to potentially read or overwrite any file on the host system as root. The issue lies in how malicious images with specific metadata can interact with the instance metadata API, bypassing previous security measures. Version 7.3.0 addresses this critical concern.

Malicious images can access host files.
Potential for unauthorized host file access.
Confirm Incus relevance and exposure.

Attack Path

How an attacker could exploit the issue

An authenticated user of the Incus system could exploit a vulnerability by uploading a specially crafted image. This image, containing a malicious `metadata.yaml` file, can be used to trick the instance metadata API into reading or overwriting any file on the host system with root privileges.

Authenticated Incus user required.
Malicious image uploaded via metadata API.
Arbitrary host file read/write as root.

Live Threat

Current exploitation, exposure, and threat context

A malicious image containing a `metadata.yaml` symlink could allow an authenticated Incus user to read or overwrite any file on the host as root when supported by the instance metadata API.

Host files could be read or overwritten.
Malicious image and metadata API access.
Full host system compromise.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in Incus impacts system container and virtual machine management, requiring attention from infrastructure and platform teams responsible for managing this technology. The first practical step is to identify all Incus deployments, assess their network reachability and criticality, and determine the accountable owner for each instance to plan remediation.

Infrastructure and platform teams should own.
Verify Incus deployment reachability and criticality.
Plan and coordinate Incus version 7.3.0 upgrade.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Incus and what is it used for?

Incus is an open-source tool designed to manage system containers and virtual machines. It provides a unified interface for users to create, run, and orchestrate these isolated environments on a host machine, acting as a manager for infrastructure resources.

How does CVE-2026-63343 manifest as a security weakness?

This vulnerability is classified as CWE-73, which involves improper control of file pathnames. Specifically, the software fails to properly validate symbolic links within an image's metadata. This allows a user to point a file path to unintended locations on the host system, bypassing previous security controls.

Do I need a specific trigger to activate this vulnerability?

Yes, an attacker must be an authenticated Incus user and perform the action of uploading or utilizing a specially crafted image containing a malicious metadata.yaml file. Simply having an Incus environment running without the introduction of such a manipulated image does not trigger the vulnerability.

Is my Incus deployment likely to be targeted over the internet?

According to Halo Surface Signal, it is unlikely. Incus is typically deployed in internal, administrative, or restricted environments rather than being exposed directly to the public internet. While it is accessible over a network, access is usually reserved for authorized personnel managing infrastructure.

When should I prioritize updating my Incus software?

You should prioritize this as soon as you have identified your active Incus instances and confirmed their ownership. The practical first step is to inventory your deployments, assess their environment, and coordinate an upgrade to version 7.3.0, which resolves the flaw.

References

github.com/lxc/incus/security/advisories/GHSA-fmjx-5j3g-997p

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.