CVE-2026-70666: high-severity vulnerability in Netflix lemur
Lemur: Server-Side Request Forgery via the ACME client following server-controlled URLs
Published · Updated
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21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.4epss 0.2%
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.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
Affected products
Netflix · lemurRelated CVEs — Netflix lemur
In the same product, most dangerous first.
CVE-2026-48508HIGHLemur: Authorization bypass in StrictRolePermission / AuthorityCreatorPermissionEPSS 0.3%CVE-2026-71308HIGHLemur: Unchecked `replaces[]` lets any user silence notifications and hijack auto-rotation for arbitrary certificatesEPSS 0.3%CVE-2026-71307HIGHLemur: Authenticated low-privilege users can read plaintext destination credentials (SFTP password / private-key passphrase) via the destinations APIEPSS 0.3%CVE-2026-55164MEDIUMLemur: Plaintext password storage in Lemur user-update pathEPSS 0.3%CVE-2026-55166CRITICALLemur: any SSO-authenticated user achieves AWS IAM compromise and permanent PKI key access via ACME acme_url SSRF and creator-equality IDOREPSS 0.3%CVE-2026-71303HIGHLemur: Incomplete fix for CVE-2026-55166 -- ACME authority update endpoint allows non-admin to replace `acme_url` with internal IP, bypassing allowlistEPSS 0.3%