Overview
A critical vulnerability (CVSS 9.9) in Incus, the system container and virtual machine manager, allows an attacker to craft a malicious container image that reads or creates and writes arbitrary files on the host system. In the worst case, this leads to arbitrary command execution (RCE) on the host. The vulnerability is tracked as CVE-2026-48749.
Affected versions: Incus prior to 7.2.0. The fix is available in Incus 7.2.0.
Vulnerability Details
Incus processes container images during instance creation or import. The vulnerability exists in the image unpacking or metadata processing pipeline, where insufficient validation of image-supplied paths allows a malicious image to reference files outside the container's intended root filesystem.
A specially crafted image can:
- Read arbitrary files on the host — by referencing host-side paths in image metadata or overlay layers.
- Write arbitrary files on the host — by placing crafted path traversal sequences in image layer archives, causing files to be written outside the container's rootfs into the host's filesystem.
Why This Leads to RCE
Writing arbitrary files to the host enables multiple code execution paths, including:
| Attack Path | Description |
|---|---|
/etc/cron.d/ write | Plant a cronjob on the host |
/root/.ssh/authorized_keys write | Add an attacker SSH key |
| Shared library overwrite | Replace a host library loaded by a privileged process |
| systemd unit write | Install a persistent service on the host |
Any of these paths can result in full host compromise.
Impact
- Arbitrary file read from the host filesystem.
- Arbitrary file write to the host filesystem.
- Remote code execution on the host via file write primitives.
- Exploitation requires the ability to cause an Incus host to import a malicious image (e.g., by controlling an image source, via a supply-chain attack on a container registry, or by direct API access to the Incus daemon).
Affected Products
| Product | Affected Versions | Fixed Version |
|---|---|---|
| Incus | < 7.2.0 | 7.2.0 |
Remediation
Update Incus to version 7.2.0 or later. The patch adds path validation and sanitization during image unpacking to ensure that no image-supplied paths can escape the container's root filesystem boundary.
# Check current Incus version
incus version
# Update via snap
snap refresh incus
# Or via apt (Zabbly repository)
apt update && apt install incusAdditional mitigations:
- Only pull container images from trusted, verified sources.
- Enforce image signing and verification where supported.
- Audit Incus daemon access controls — the attack surface is reduced if only trusted users can trigger image imports.