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

{
  "id": "ab57affc11963123cb05420734c3a0adf919b8a5ff2cc12c73dc44bd4168fb00",
  "url": "https://osv.dev/vulnerability/CVE-2026-71303",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Lemur: Incomplete fix for CVE-2026-55166 -- ACME authority update endpoint allows non-admin to replace `acme_url` with internal IP, bypassing allowlist",
    "summary": "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.",
    "evidence": "osv:CVE-2026-71303",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-71303",
      "aliases": [
        "CVE-2026-71303",
        "GHSA-v5rc-cpwc-cfpr",
        "PYSEC-2026-3679"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/netflix/lemur",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "726506d15a6da8d9bcf5c39b4dc0c95535cf03c0"
                },
                {
                  "fixed": "edca0390f930344d65ff4ca37a669c2320e3dfad"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.9.3"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "edca0390f930344d65ff4ca37a669c2320e3dfad"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "726506d15a6da8d9bcf5c39b4dc0c95535cf03c0"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v1.9.3"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v1.9.2",
            "v1.9.1",
            "v1.9.0",
            "v1.8.2",
            "v1.8.1",
            "v1.8.0",
            "v1.7.0",
            "v1.6.0",
            "v1.5.0",
            "v1.4.0",
            "v1.3.2",
            "v1.3.1",
            "v1.3.0",
            "v1.2.0",
            "v1.1.0",
            "v1.0.0",
            "v0.11.0",
            "v0.10.0",
            "v0.9.0",
            "v0.8.1",
            "0.8.0",
            "0.7.0",
            "0.6.0",
            "0.5.0",
            "0.4.0",
            "0.3.0",
            "0.2.2",
            "0.2.1",
            "0.2",
            "0.1.5",
            "0.1.4",
            "0.1.3",
            "0.1.2",
            "0.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-71303.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:27.108763964Z",
      "provider": "osv",
      "references": [
        "https://github.com/Netflix/lemur/releases/tag/v1.9.3",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/71xxx/CVE-2026-71303.json",
        "https://github.com/Netflix/lemur/security/advisories/GHSA-v5rc-cpwc-cfpr",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-71303",
        "https://github.com/Netflix/lemur/commit/edca0390f930344d65ff4ca37a669c2320e3dfad"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-918"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/71xxx/CVE-2026-71303.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-71303",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 493933,
  "published_at": "2026-08-18T19:03:55.524+00:00"
}