CVE-2026-71303: netflix lemur Server-Side Request Forgery (SSRF)

Vulnerability summary

CVE-2026-71303 is a high (CVSS 7.7) Server-Side Request Forgery (SSRF) vulnerability in netflix lemur. EPSS estimates a 0.28% chance of exploitation in the next 30 days, higher than 18.8% of scored vulnerabilities.

Timeline

1. 18-08-2026
   PublishedVulnerability first disclosed.
2. 18-08-2026
   Last modifiedVulnerability information updated.

Description

Lemur manages TLS certificate creation. Prior to 1.9.3, _validate_acme_url enforced ACME_DIRECTORY_HOST_ALLOWLIST when an authority was created, but PUT /api/1/authorities/ passed options to lemur/authorities/service.py without applying the same check. A user holding an authority role could replace the stored acme_url with an internal service or instance-metadata URL such as 169.254.169.254. The next issuance operation loaded that value and passed it to ClientV2.get_directory, causing an outbound request from the Lemur backend. This bypassed the creation-time mitigation for CVE-2026-55166 and could expose internal services or cloud metadata. The fix revalidates acme_url whenever authority options are updated. This issue is fixed in version 1.9.3.

• CWE-918Server-Side Request Forgery (SSRF)The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.