hex_core's default HTTP adapter doesn't verify TLS certificates on OTP 24 and 25

{
  "id": "1ab6cb3c2f9ea51c7f32a15de0dd669fa49c010c68c77217855af29a80fc80ef",
  "url": "https://osv.dev/vulnerability/CVE-2026-103502",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "hex_core's default HTTP adapter doesn't verify TLS certificates on OTP 24 and 25",
    "summary": "Improper Certificate Validation vulnerability in hexpm hex_core allows an attacker who can intercept HTTPS connections to impersonate hex.pm, repo.hex.pm or any other repository or API server to programs that use hex_core's default HTTP adapter on Erlang/OTP 24, or on OTP 25 when the operating system's CA certificates can't be loaded. hex_core:default_config/0 selects the built-in hex_http_httpc adapter. For an HTTPS request whose adapter config has no ssl option, hex_http_httpc:http_options/2 builds options that verify the server certificate against public_key:cacerts_get/0. When that call raises, the adapter prints a warning and sends the request without ssl options, so httpc uses the defaults of the ssl application, which before OTP 26 don't verify the server certificate. public_key:cacerts_get/0 doesn't exist on OTP 24, so every HTTPS request falls back there, and on OTP 25 it raises when no CA store is found. hex_core versions before 0.11.0 never set ssl options, so they don't verify the server certificate on OTP 25 and earlier whether or not a CA store is found. The fallback was intended and documented, but the documentation didn't make clear that it meant no certificate verification. Since hex_core 0.8.2 the README has warned that the built-in httpc adapter \"has insecure default settings\" and recommended other HTTP clients, and the adapter prints \"using default ssl options which are insecure\" on every request that falls back. hex_core 0.11.0 added certificate verificat",
    "evidence": "osv:CVE-2026-103502",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-103502",
      "aliases": [
        "CVE-2026-103502",
        "EEF-CVE-2026-103502",
        "GHSA-p26c-h8c2-rwqj"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/hexpm/hex_core",
              "type": "GIT",
              "events": [
                {
                  "introduced": "fbb6d9de472e5edb8d6fb6b32a91cb266137892e"
                },
                {
                  "fixed": "b7b3a42defb4ed8e20a5c68a4412ce68a95b7938"
                },
                {
                  "introduced": "a2c868584104380dcd0d712594417f92179285e8"
                },
                {
                  "fixed": "a036d3574bfe186bebbbac503475f327c7ea5f38"
                },
                {
                  "fixed": "fbb6d9de472e5edb8d6fb6b32a91cb266137892e"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "fbb6d9de472e5edb8d6fb6b32a91cb266137892e"
                      },
                      {
                        "fixed": "b7b3a42defb4ed8e20a5c68a4412ce68a95b7938"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0.1.0"
                      },
                      {
                        "fixed": "0.20.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "fixed": "fbb6d9de472e5edb8d6fb6b32a91cb266137892e"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "b7b3a42defb4ed8e20a5c68a4412ce68a95b7938"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v0.19.0",
            "v0.18.0",
            "v0.17.0",
            "v0.16.1",
            "v0.16.0",
            "v0.15.0",
            "v0.14.1",
            "v0.14.0",
            "v0.13.0",
            "v0.12.2",
            "v0.12.1",
            "v0.12.0",
            "v0.11.0",
            "v0.10.3",
            "v0.10.2",
            "v0.10.1",
            "v0.10.0",
            "v0.9.0",
            "v0.8.4",
            "v0.8.3",
            "v0.8.2",
            "v0.8.1",
            "v0.8.0",
            "v0.7.1",
            "v0.7.0",
            "v0.6.9",
            "v0.6.8",
            "v0.6.7",
            "v0.6.6",
            "v0.6.5",
            "v0.6.4",
            "v0.6.3",
            "v0.6.1",
            "v0.5.0",
            "v0.6.0",
            "v0.4.0",
            "v0.3.0",
            "v0.2.1",
            "v0.2.0",
            "v0.1.1",
            "v0.1.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-103502.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:23.519093346Z",
      "provider": "osv",
      "references": [
        "https://cna.erlef.org/cves/CVE-2026-103502.html",
        "https://github.com",
        "https://osv.dev/vulnerability/EEF-CVE-2026-103502",
        "https://repo.hex.pm",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/103xxx/CVE-2026-103502.json",
        "https://github.com/hexpm/hex_core/security/advisories/GHSA-p26c-h8c2-rwqj",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-103502",
        "https://github.com/hexpm/hex_core/commit/b7b3a42defb4ed8e20a5c68a4412ce68a95b7938",
        "https://github.com/hexpm/hex_core/commit/fbb6d9de472e5edb8d6fb6b32a91cb266137892e",
        "https://github.com/hexpm/hex_core"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-295",
          "CWE-636"
        ],
        "cna_assigner": "EEF",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/103xxx/CVE-2026-103502.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-103502",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 490158,
  "published_at": "2026-10-12T13:15:29.04+00:00"
}