What’s Vulnerable › Vulnerabilities

CVE-2026-70666: Lemur: Server-Side Request Forgery via the ACME client following server-controlled URLs

• Severity: high (CVSS 7.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-18 · updated 2026-10-22
• Weakness: CWE-918

Description

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.

Affected products

• Netflix lemur: before 1.9.3

References

• https://github.com/Netflix/lemur/commit/6dcb19b6d6004e97796d6a0344b130b2ba57f050
• https://github.com/Netflix/lemur/releases/tag/v1.9.3
• https://github.com/Netflix/lemur/security/advisories/GHSA-xpmj-wjcp-6pww

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