CVE-2026-55166
CriticalCVSS 9.9Summary
Lemur before version 1.9.2 has a vulnerability that allows authenticated users to influence the ACME authority URL (acme_url) without effective server-side destination restriction, enabling SSRF attacks on internal services or cloud metadata. Additionally, there is an authorization weakness that could preserve access to private keys after ownership changes.
Risk Assessment
The attack could lead to exposure of cloud credentials and long-term access to PKI private keys, posing a serious threat to infrastructure security.
Recommendation
Update Lemur to version 1.9.2 or later, which includes fixes (ACME_DIRECTORY_HOST_ALLOWLIST and enriched key export audits).
Original NVD description (English source)
Lemur manages TLS certificate creation. Prior to 1.9.2, authenticated users could influence an ACME authority acme_url without an effective server-side destination restriction and trigger AcmeHandler.setup_acme_client 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 export_private_key audit context to distinguish that access path. Together, the acme_url server-side request forgery and authorization weakness could expose cloud credentials and long-lived PKI private-key access. The fix adds ACME_DIRECTORY_HOST_ALLOWLIST validation and enriches key-export audit events with creator and current-owner context. This issue is fixed in version 1.9.2.