LXD's PKI mode activates when a server.ca file is present in LXD_DIR at startup, requiring clients to present CA-signed certificates. The configuration option core.trust_ca_certificates defaults to false, meaning certificate restrictions should be enforced. However, due to a flaw introduced during authorization refactoring, restricted client certificates are not honored and are granted full access to LXD when core.trust_ca_certificates is false. A cherry-pick fix addressed the issue when core.trust_ca_certificates is true but did not fix the false case. This results in privilege escalation for restricted certificates in PKI mode. The vulnerability is tracked as CVE-2024-6219.

Clients with restricted TLS certificates can bypass their restrictions and gain full access to LXD when PKI mode is enabled and core.trust_ca_certificates is false. This leads to unauthorized privilege escalation within LXD. However, the impact is mitigated by the fact that PKI mode is not the default configuration and users enabling it generally enable core.trust_ca_certificates, which grants full access to all CA-signed clients anyway.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Users should verify their LXD configuration, especially the core.trust_ca_certificates setting, and avoid running LXD in PKI mode with core.trust_ca_certificates set to false. Monitor official LXD releases and advisories for patches addressing this issue. The vendor has applied a partial fix for the case when core.trust_ca_certificates is true, but the false case remains unaddressed.