Custom cacerts or cacertfile do not restrict trust to the pinned CA in hackney

{
  "id": "583efe676f02f80e84d7085824d51fe332a8892e403b4b3570bcc4c2050e9498",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-115693",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Custom cacerts or cacertfile do not restrict trust to the pinned CA in hackney",
    "summary": "Improper Certificate Validation vulnerability in hackney_ssl in benoitc hackney allows an on-path attacker to impersonate a server pinned to a private certificate authority via a certificate chain that ends in a publicly trusted root. hackney adds {partial_chain, fun hackney_ssl:partial_chain/1} to every verify_peer configuration. The callback returns any certificate in the peer chain whose public key matches a root in the bundled certifi store as the trust anchor, and OTP honours that callback over the configured cacerts. hackney_ssl:merge_ssl_opts/3 kept the callback when the caller replaced the trust store with cacerts or cacertfile in ssl_options, so a connection pinned to a private CA still accepted any chain that carried a publicly trusted root. The hostname check still applies, so the attacker needs a publicly trusted certificate for the pinned hostname. This issue affects hackney: from 1.24.0 before 4.9.0.",
    "evidence": "cve:CVE-2026-115693",
    "products": [
      {
        "name": {
          "value": "hackney",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      },
      {
        "name": {
          "value": "hackney",
          "evidence": "/containers/cna/affected/1/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-115693",
      "aliases": [
        "CVE-2026-115693"
      ],
      "metrics": [
        {
          "format": "CVSS",
          "cvssV4_0": {
            "Safety": "NOT_DEFINED",
            "version": "4.0",
            "Recovery": "NOT_DEFINED",
            "baseScore": 9.1,
            "Automatable": "NOT_DEFINED",
            "attackVector": "NETWORK",
            "baseSeverity": "CRITICAL",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
            "providerUrgency": "NOT_DEFINED",
            "userInteraction": "NONE",
            "attackComplexity": "HIGH",
            "attackRequirements": "PRESENT",
            "privilegesRequired": "NONE",
            "subIntegrityImpact": "NONE",
            "vulnIntegrityImpact": "HIGH",
            "subAvailabilityImpact": "NONE",
            "vulnAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "vulnConfidentialityImpact": "HIGH",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "affected": [
        {
          "cpes": [
            "cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"
          ],
          "repo": "https://github.com/benoitc/hackney",
          "vendor": "benoitc",
          "modules": [
            "hackney_ssl"
          ],
          "product": "hackney",
          "versions": [
            {
              "status": "affected",
              "version": "1.24.0",
              "lessThan": "4.9.0",
              "versionType": "semver"
            }
          ],
          "packageURL": "pkg:hex/hackney",
          "packageName": "hackney",
          "programFiles": [
            "src/hackney_ssl.erl"
          ],
          "collectionURL": "https://repo.hex.pm",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "hackney_ssl:ssl_opts/2"
            },
            {
              "name": "hackney_ssl:merge_ssl_opts/3"
            },
            {
              "name": "hackney_ssl:partial_chain/1"
            }
          ]
        },
        {
          "cpes": [
            "cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"
          ],
          "repo": "https://github.com/benoitc/hackney",
          "vendor": "benoitc",
          "modules": [
            "hackney_ssl"
          ],
          "product": "hackney",
          "versions": [
            {
              "status": "affected",
              "version": "d8a9afcf5c3849904274e2eba1df56c63d1a1a0c",
              "lessThan": "915eb5737e9c489d8fc22eec8cdae30e9b027be4",
              "versionType": "git"
            }
          ],
          "packageURL": "pkg:github/benoitc/hackney",
          "packageName": "benoitc/hackney",
          "programFiles": [
            "src/hackney_ssl.erl"
          ],
          "collectionURL": "https://github.com",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "hackney_ssl:ssl_opts/2"
            },
            {
              "name": "hackney_ssl:merge_ssl_opts/3"
            },
            {
              "name": "hackney_ssl:partial_chain/1"
            }
          ]
        }
      ],
      "modified": "2026-10-26T13:49:29.374Z",
      "provider": "cve",
      "references": [
        "https://github.com/benoitc/hackney/pull/978",
        "https://cna.erlef.org/cves/CVE-2026-115693.html",
        "https://osv.dev/vulnerability/EEF-CVE-2026-115693",
        "https://github.com/benoitc/hackney/releases/tag/4.9.0",
        "https://github.com/benoitc/hackney/commit/d8a9afcf5c3849904274e2eba1df56c63d1a1a0c",
        "https://github.com/benoitc/hackney/commit/915eb5737e9c489d8fc22eec8cdae30e9b027be4"
      ],
      "provider_metadata": {
        "cna": {
          "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
          "shortName": "EEF",
          "dateUpdated": "2026-10-26T13:49:29.374Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-115693",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/containers/cna/metrics"
  },
  "source_id": "core-cve",
  "document_id": 307255,
  "published_at": "2026-10-26T13:49:29.374+00:00"
}