CVE-2026-63300: An improper validation vulnerability in the instancePostMigration function in lxd/instance_post.go of LXD allo

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CRITICAL 9.9UPGRADE

CVE-2026-63300 is a critical-severity flaw (CVSS 9.9) affecting lxd. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.dev

Why this priority

Critical severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	9.9 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.5% (top 55%)
CISA exploited list	No
Weakness	CWE-862
Published	2026-08-12
Last modified	2026-10-23

Publisher (CNA): Canonical Ltd. · Vendor: canonical

Last updated 2026-10-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-12 20:17 UTCPublished CVE record published
2026-10-23 19:10 UTCUpdated Record last modified

canonical lxd UPGRADE

Affected: >= 5.0.0 and < 5.0.8 · >= 5.1 and < 5.21.6 · >= 6.0 and < 6.10

Fixed in: 5.0.8, 5.21.6, 6.10

Safe to downgrade to: a release before 5.0.0

1. Check installed version

apt-cache policy lxd || rpm -q lxd || lxd --version

2. UPGRADE to 5.0.8 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade lxd

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade lxd

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 5.0.0 (Debian / Ubuntu)

apt-cache madison lxd sudo apt install lxd=<VERSION_BEFORE_5.0.0> sudo apt-mark hold lxd

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list lxd sudo dnf downgrade lxd-<VERSION_BEFORE_5.0.0> sudo dnf versionlock add lxd

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

Fedora 46 · rubygem-eventmachine · FIXED · 1.2.7-37.fc46 · FEDORA-2026-7194c202a2 · source

sudo dnf upgrade --advisory=FEDORA-2026-7194c202a2

Debian 12 · lxd · NO FIX YET

Debian 13 · lxd · NO FIX YET

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: github.com/canonical/lxd/security/advisories/GHSA-5g5r-wh97-qcq2

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-63300?

lxd: upgrade to 5.0.8, 5.21.6, 6.10. Exact commands for each OS are on this page.

Is CVE-2026-63300 being exploited?

CVE-2026-63300 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-63300 affect?

CVE-2026-63300 affects lxd. Severity is critical (CVSS 9.9). 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 restri

How urgent is CVE-2026-63300?

Priority 51/100. Critical severity; Public exploit reference

Related CVEs

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CVE-2025-54289 HIGH 8.1 UPGRADE Privilege Escalation in operations API in Canonical LXD <6.5 on multiple platforms allows attacker with read p
CVE-2026-63294 CRITICAL 9.9 UPGRADE A link following vulnerability in LXD allows an attacker to achieve root command execution on the host system
CVE-2026-63298 CRITICAL 9.9 UPGRADE An improper neutralization of special elements vulnerability in LXD's NVIDIA instance configuration handling a
CVE-2026-63293 CRITICAL 9.9 UPGRADE A link following vulnerability in LXD allows an attacker to achieve arbitrary file read and write operations o

References

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