What’s Vulnerable › Vulnerabilities

CVE-2026-71303: Lemur: Incomplete fix for CVE-2026-55166 -- ACME authority update endpoint allows non-admin to replace `acme_url` with internal IP, bypassing allowlist

• Severity: high (CVSS 7.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% 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, _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.

Affected products

• Netflix lemur: before 1.9.3

References

• https://github.com/Netflix/lemur/commit/edca0390f930344d65ff4ca37a669c2320e3dfad
• https://github.com/Netflix/lemur/releases/tag/v1.9.3
• https://github.com/Netflix/lemur/security/advisories/GHSA-v5rc-cpwc-cfpr
• https://github.com/Netflix/lemur/security/advisories/GHSA-v5rc-cpwc-cfpr

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