CVE-2026-55166

Lemur manages TLS certificate creation. Prior to 1.9.2, authenticated users could influence an ACME authority acmeurl without an effective server-side destination restriction and trigger AcmeHandler.setupacmeclient to make backend requests. An attacker could target cloud instance metadata or internal services from Lemur network context, potentially obtaining credentials available to the host. The advisory also identifies creator-equality authorization behavior that could preserve access to certificate key material after ownership or role changes, with insufficient exportprivatekey audit context to distinguish that access path. Together, the acmeurl server-side request forgery and authorization weakness could expose cloud credentials and long-lived PKI private-key access. The fix adds ACMEDIRECTORYHOST_ALLOWLIST validation and enriches key-export audit events with creator and current-owner context. This issue is fixed in version 1.9.2.