LXD Auth Bypass via TOCTOU in crossproject instance copy
CVE-2026-63297 Published on August 12, 2026
Cross-project instance copy bypasses target project restrictions via TOCTOU in config merge
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.
Vulnerability Analysis
CVE-2026-63297 can be exploited with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be critical as this vulnerability has a high impact to the confidentiality, integrity and availability of this component.
Weakness Types
What is a TOCTTOU Vulnerability?
The software checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the software to perform invalid actions when the resource is in an unexpected state. This weakness can be security-relevant when an attacker can influence the state of the resource between check and use. This can happen with shared resources such as files, memory, or even variables in multithreaded programs.
CVE-2026-63297 has been classified to as a TOCTTOU vulnerability or weakness.
What is an AuthZ Vulnerability?
The software performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.
CVE-2026-63297 has been classified to as an AuthZ vulnerability or weakness.
Products Associated with CVE-2026-63297
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Affected Versions
Canonical LXD:- Version 5.0.0 and below 5.0.8 is affected.
- Version 5.21.0 and below 5.21.6 is affected.