Hex writes unverified package tarballs to standard output in mix hex.package fetch

{
  "id": "2ced1bdec5866fac97207508b0491c41e21a49ecf5ff5135aace4fa6aede3288",
  "url": "https://osv.dev/vulnerability/EEF-CVE-2026-105280",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Hex writes unverified package tarballs to standard output in mix hex.package fetch",
    "summary": "## Summary Improper Validation of Integrity Check Value vulnerability in hexpm hex allows a package mirror to substitute the tarball that `mix hex.package fetch PACKAGE VERSION --output -` writes to standard output. Hex compares a fetched tarball's inner and outer checksums with the repository's signed registry before writing it to a file or unpacking it. The standard output branch of `mix hex.package fetch` writes the bytes returned by `Hex.SCM.fetch/3` without that comparison, and `Hex.SCM.fetch/3` doesn't verify freshly downloaded tarballs itself. When a mirror configured with `HEX_MIRROR_URL` or `mirror_url` serves altered bytes, the command prints them and exits successfully, while the same fetch with `--output FILE` fails with a checksum mismatch. Hex also prints diagnostics to standard output while the command runs: the body of a failed HTTP response from the update check or a registry fetch, and API warnings from the `x-hex-message` header. A mirror that answers one of those requests with an error whose body is a tar archive gets that archive written to standard output ahead of the verified tarball, so a pipeline that unpacks standard output extracts the mirror's files. This happens even when the checksum check then fails, because the archive is already on standard output. This issue affects hex: from 0.20.2 before 2.5.2. ## Details 1. `mix hex.package fetch PACKAGE VERSION --output -` calls `fetch_tarball!/3`, which calls `Hex.SCM.fetch/3`. 2. For a fresh download, `",
    "evidence": "osv:EEF-CVE-2026-105280",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "EEF-CVE-2026-105280",
      "aliases": [
        "CVE-2026-105280",
        "EEF-CVE-2026-105280",
        "GHSA-98jr-23pm-vj7c"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/hexpm/hex",
              "type": "GIT",
              "events": [
                {
                  "introduced": "d1f5a085d9d4748e1f7d195e4bc39ebd77c28d9c"
                },
                {
                  "fixed": "8a14632ca6ba8a8afd2a3f2098bc267c13e13d93"
                },
                {
                  "fixed": "69489f8b74213f03db10169e6e5407e6d5fee512"
                }
              ]
            }
          ],
          "versions": [
            "v2.5.1",
            "v2.5.0",
            "v2.2.2",
            "v2.4.2",
            "v2.4.1",
            "v2.4.0",
            "v2.2.1",
            "v2.2.0",
            "v2.0.6",
            "v2.1.1",
            "v0.21.3",
            "v2.1.0",
            "v2.0.5",
            "v2.0.4",
            "v2.0.3",
            "v2.0.2",
            "v2.0.1",
            "v2.0.0",
            "v1.0.1",
            "v1.0.0",
            "v0.21.2",
            "v0.21.1",
            "v0.21.0",
            "v0.20.5",
            "v0.20.4",
            "v0.20.3",
            "v0.20.2"
          ],
          "database_specific": {
            "source": "https://cna.erlef.org/osv/EEF-CVE-2026-105280.json"
          }
        }
      ],
      "modified": "2026-10-12T15:56:08.997030070Z",
      "provider": "osv",
      "references": [
        "https://github.com/hexpm/hex/security/advisories/GHSA-98jr-23pm-vj7c",
        "https://cna.erlef.org/cves/CVE-2026-105280.html",
        "https://github.com/hexpm/hex/commit/d1f5a085d9d4748e1f7d195e4bc39ebd77c28d9c",
        "https://github.com/hexpm/hex/commit/8a14632ca6ba8a8afd2a3f2098bc267c13e13d93",
        "https://github.com/hexpm/hex/commit/69489f8b74213f03db10169e6e5407e6d5fee512"
      ],
      "provider_metadata": {
        "cpe_ids": [
          "cpe:2.3:a:hexpm:hex:*:*:*:*:*:*:*:*"
        ],
        "cwe_ids": [
          "CWE-354"
        ],
        "capec_ids": [
          "CAPEC-186"
        ]
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-105280",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 300017,
  "published_at": "2026-10-12T15:30:14.126+00:00"
}