CVE-2026-63297: Cross-project instance copy bypasses target project restrictions via TOCTOU in config merge

Severity: critical (CVSS 9.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-08-12 · updated 2026-10-24
Weakness: CWE-367

Description

An authorization bypass vulnerability in LXD due to a timing flaw during configuration merging allows an authenticated attacker to bypass target project restrictions during cross-project instance copies. When copying an instance to a target project, LXD performs restriction checks before configuration merging is complete, creating a time-of-check to time-of-use (TOCTOU) condition. An attacker can exploit this flaw to copy instances with disallowed high-privilege configurations into restricted projects, bypassing security controls.

Affected products

Canonical LXD: from 5.0.0 before 5.0.8; from 5.1 before 5.21.6; from 6.0 before 6.9 — fixed in 5.0.8, 5.21.6, 6.9

How to fix

Upgrade to a fixed version: Canonical LXD 5.0.8, 5.21.6, 6.9. Check the vendor advisory for mitigations.

References

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