Auth bypass in Canonical Lxd
CVE-2026-63300
An improper validation vulnerability in the instancePostMigration function in lxd/instance_post.go of LXD allows an authenticated attacker with can_create_instances permissions on a restricted project to bypass project-level security restrictions. When migrating an instance between projects, LXD fails to validate the instance's configuration against the target project's enforced restrictions (such as restricted.containers.lowlevel, restricted.devices.*, and restricted.networks.access). An attacker can exploit this by creating a disallowed or high-privilege instance in an unrestricted project and subsequently moving it into the restricted project.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.9 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.005 (43.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 43.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
- Canonical Lxd — versions 5.0.0, 5.21.0, 6.0
Weakness classification (CWE)
References
- github.com/canonical/lxd/security/advisories/GHSA-5g5r-wh97-qcq2 (Exploit, vendor-advisory, Mitigation, vdb-entry, Vendor Advisory)
- github.com/canonical/lxd/pull/18651 (Patch, patch)
- github.com/canonical/lxd/pull/18605 (Exploit, Patch, patch)
Frequently asked questions
- What is CVE-2026-63300?
- CVE-2026-63300 is a critical-severity vulnerability in Canonical Lxd, classified under Missing Authorization. CVSS score: 9.9/10. Published 2026-08-12.
- How severe is CVE-2026-63300?
- Critical severity. CVSS v3 base score is 9.9 out of 10.