Incus is a system container and virtual machine manager. Incus instances have an option to provide credentials to systemd in the guest. For containers, this is handled through a shared directory. Prior to version 6.23.0, an attacker can set a configuration key named something like `systemd.credential.../../../../../../root/.bashrc` to cause Incus to write outside of the `credentials` directory associated with the container. This makes use of the fact that the Incus syntax for such credentials is `systemd.credential.XYZ` where `XYZ` can itself contain more periods. While it's not possible to read any data this way, it's possible to write to arbitrary files as root, enabling both privilege escalation and denial of service attacks. Version 6.23.0 fixes the issue.

Incus is a system container and virtual machine manager. Prior to version 6.23.0, the web server spawned by `incus webui` incorrectly validates the authentication token such that an invalid value will be accepted. `incus webui` runs a local web server on a random localhost port. For authentication, it provides the user with a URL containing an authentication token. When accessed with that token, Incus creates a cookie persisting that token without needing to include it in subsequent HTTP requests. While the Incus client correctly validates the value of the cookie, it does not correctly validate the token when passed int the URL. This allows for an attacker able to locate and talk to the temporary web server on localhost to have as much access to Incus as the user who ran `incus webui`. This can lead to privilege escalation by another local user or an access to the user's Incus instances and possibly system resources by a remote attack able to trick the local user into interacting with the Incus UI web server. Version 6.23.0 patches the issue.

Incus is a system container and virtual machine manager. Prior to version 6.23.0, a specially crafted storage bucket backup can be used by an user with access to Incus' storage bucket feature to crash the Incus daemon. Repeated use of this attack can be used to keep the server offline causing a denial of service of the control plane API. This does not impact any running workload, existing containers and virtual machines will keep operating. Version 6.23.0 fixes the issue.

Incus is a system container and virtual machine manager. Prior to version 6.23.0, instance template files can be used to cause arbitrary read or writes as root on the host server. Incus allows for pongo2 templates within instances which can be used at various times in the instance lifecycle to template files inside of the instance. This particular implementation of pongo2 within Incus allowed for file read/write but with the expectation that the pongo2 chroot feature would isolate all such access to the instance's filesystem. This was allowed such that a template could theoretically read a file and then generate a new version of said file. Unfortunately the chroot isolation mechanism is entirely skipped by pongo2 leading to easy access to the entire system's filesystem with root privileges. Version 6.23.0 patches the issue.

Incus is a system container and virtual machine manager. Incus provides an API to retrieve VM screenshots. That API relies on the use of a temporary file for QEMU to write the screenshot to which is then picked up and sent to the user prior to deletion. As versions prior to 6.23.0 use predictable paths under /tmp for this, an attacker with local access to the system can abuse this mechanism by creating their own symlinks ahead of time. On the vast majority of Linux systems, this will result in a "Permission denied" error when requesting a screenshot. That's because the Linux kernel has a security feature designed to block such attacks, `protected_symlinks`. On the rare systems with this purposefully disabled, it's then possible to trick Incus intro truncating and altering the mode and permissions of arbitrary files on the filesystem, leading to a potential denial of service or possible local privilege escalation. Version 6.23.0 fixes the issue.

Incus is a system container and virtual machine manager. Prior to version 6.23.0, a lack of validation of the image fingerprint when downloading from simplestreams image servers opens the door to image cache poisoning and under very narrow circumstances exposes other tenants to running attacker controlled images rather than the expected one. Version 6.23.0 patches the issue.

Incus is a system container and virtual machine manager. In versions 6.20.0 and below, a user with the ability to launch a container with a custom YAML configuration (e.g a member of the ‘incus’ group) can create an environment variable containing newlines, which can be used to add additional configuration items in the container’s lxc.conf due to newline injection. This can allow adding arbitrary lifecycle hooks, ultimately resulting in arbitrary command execution on the host. Exploiting this issue on IncusOS requires a slight modification of the payload to change to a different writable directory for the validation step (e.g /tmp). This can be confirmed with a second container with /tmp mounted from the host (A privileged action for validation only). A fix is planned for versions 6.0.6 and 6.21.0, but they have not been released at the time of publication.

Incus is a system container and virtual machine manager. Versions 6.21.0 and below allow a user with the ability to launch a container with a custom image (e.g a member of the ‘incus’ group) to use directory traversal or symbolic links in the templating functionality to achieve host arbitrary file read, and host arbitrary file write. This ultimately results in arbitrary command execution on the host. When using an image with a metadata.yaml containing templates, both the source and target paths are not checked for symbolic links or directory traversal. This can also be exploited in IncusOS. A fix is planned for versions 6.0.6 and 6.21.0, but they have not been released at the time of publication.