Authenticated SSRF via server-controlled ACME URLs
Published Aug 18, 2026 · Updated Aug 19, 2026
Server-side request forgery in Netflix Lemur before 1.9.3 allows remote authenticated users to reach internal services via ACME updates. PUT /api/1/authorities/ accepted a replacement acme_url without rerunning the directory-host allowlist, and the ACME ClientV2 then followed newNonce, newOrder, authorizations, and finalize URLs returned by that attacker-controlled ACME server without requiring the host to stay pinned to the configured directory. Exploitation requires an existing ACME authority and a user in that authority's role, but not global administrator access; the resulting JWS-signed requests can be sent to cloud metadata or other internal HTTP endpoints.
Summary
What happened
Server-side request forgery in Netflix Lemur before 1.9.3 allows remote authenticated users to reach internal services via ACME updates. PUT /api/1/authorities/ accepted a replacement acme_url without rerunning the directory-host allowlist, and the ACME ClientV2 then followed newNonce, newOrder, authorizations, and finalize URLs returned by that attacker-controlled ACME server without requiring the host to stay pinned to the configured directory. Exploitation requires an existing ACME authority and a user in that authority's role, but not global administrator access; the resulting JWS-signed requests can be sent to cloud metadata or other internal HTTP endpoints.
The record
- CVE
- CVE-2026-70666
- Published
- Aug 18, 2026
- Updated
- Aug 19, 2026
- Vendor
- Netflix
- Product
- Lemur
- Classifications
- CWE-918
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 18, 2026CVE publishedPublication date reported by the CVE source.
- Aug 19, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 1.9.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-xpmj-wjcp-6pww Steps to Reproduceproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo