CVE-2026-70666
HighCVSS 7.4Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
Lemur before version 1.9.3 allowed an authority-role user to update acme_url without revalidation and direct the ACME client to an attacker-controlled server. That server could return URLs (newNonce, newOrder, authorizations, finalize) pointing to internal services or cloud metadata, and Lemur followed them without host validation. The issue is fixed in version 1.9.3.
Risk Assessment
The risk includes sending JWS-signed requests to internal services or cloud metadata, potentially leading to unauthorized access or privilege escalation. However, the attack requires authority permissions.
Recommendation
Upgrade Lemur to version 1.9.3 or later and limit the number of users with authority role. Also monitor outbound traffic from the Lemur server.
Original NVD description (English source)
Lemur manages TLS certificate creation. Prior to 1.9.3, an authority-role member could update acme_url through PUT /api/1/authorities/ without revalidation and direct setup_acme_client_no_retry to an attacker-controlled ACME server. ACME directory and order responses contain newNonce, newOrder, authorizations, and finalize URLs chosen by that server. The Lemur ClientV2 followed those URLs without requiring their host to match the configured directory host, allowing JWS-signed requests to internal services or cloud metadata endpoints. The issue required an ACME authority and a user authorized for that authority, but did not require global administrator privileges. The fix revalidates updates and introduces _PinnedClientNetwork to enforce a single allowed host for the complete ACME flow. This issue is fixed in version 1.9.3.