Malicious code in web3-signer-kit (RubyGems)

{
  "id": "aacc486583763c620439edd460f4e0e40ac3f632f0dfefda470bf245c5778503",
  "url": "https://osv.dev/vulnerability/MAL-2026-17801",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Malicious code in web3-signer-kit (RubyGems)",
    "summary": "--- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (fe57c8011ef7048ef33ccdb828615b8efd9ab10799a2a730d12c2d854c2e0895) The gem's extconf.rb decodes a base64 literal and eval's it at `gem install` time inside a double-forked, session-detached child whose stdio is redirected to /dev/null. The decoded payload opens a TCPSocket to 45.138.12.177:8089 and bridges a `/bin/sh` process over that socket via IO.popen + IO.copy_stream, yielding full-host remote code execution for the operator of that endpoint. Execution is gated by sandbox-evasion checks that skip CI, ephemeral/short-uptime hosts, analyst-style usernames, and analysis paths, and requires developer artifacts (~/.ssh, ~/.gitconfig, ~/.gem/credentials) to be present before firing; a randomized sleep of 1200+rand(1200) seconds further delays detonation. The package has no legitimate functionality: metadata describes it as a 'web3 signer kit' while the README advertises `bitcoin-rpc-lite`, the library exposes only stub methods (`build_id`, `healthy?`), and extconf.rb calls `create_makefile('bitcoin_rpc_lite_native')` with no C sources shipped. The entire gem is a decoy wrapper around the dropper in extconf.rb.",
    "evidence": "osv:MAL-2026-17801",
    "products": [
      {
        "name": {
          "value": "web3-signer-kit",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "0.9.1",
            "evidence": "/affected/0/versions"
          }
        ]
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "MAL-2026-17801",
      "aliases": [
        "MAL-2026-17801"
      ],
      "affected": [
        {
          "package": {
            "name": "web3-signer-kit",
            "purl": "pkg:gem/web3-signer-kit",
            "ecosystem": "RubyGems"
          },
          "versions": [
            "0.9.1"
          ],
          "database_specific": {
            "cwes": [
              {
                "name": "Embedded Malicious Code",
                "cweId": "CWE-506",
                "description": "The product contains code that appears to be malicious in nature."
              }
            ],
            "source": "https://github.com/ossf/malicious-packages/blob/main/osv/malicious/rubygems/web3-signer-kit/MAL-2026-17801.json",
            "indicators": {
              "evidence_files": [
                {
                  "path": "ext/web3_signer_kit/extconf.rb",
                  "tlsh": "9751775acf8359e55aa1c0c045798012faa3ab0a50646875f3ee0868ff59b26c0f12fe",
                  "sha256": "10218e975f54a4f11fe3954e1b584a5f05054003bf5773c3c2b8cceaa74ba763"
                },
                {
                  "path": "metadata.yaml",
                  "tlsh": "f711c3c075c7ed3af922d2e6dc403303e362d60cbdd62a0049d7819983855aa274b165",
                  "sha256": "40a2b5118fb3a4084fc2d2a42c90a86ade8013cc95fa07455fca279dddf11499"
                }
              ]
            }
          }
        }
      ],
      "modified": "2026-10-11T14:30:09.723249551Z",
      "provider": "osv",
      "references": [
        "https://rubygems.org/gems/web3-signer-kit/versions/0.9.1"
      ],
      "provider_metadata": {
        "malicious-packages-origins": [
          {
            "id": "IN-MAL-2026-021367",
            "sha256": "fe57c8011ef7048ef33ccdb828615b8efd9ab10799a2a730d12c2d854c2e0895",
            "source": "amazon-inspector",
            "versions": [
              "0.9.1"
            ],
            "import_time": "2026-10-11T14:17:59.748018032Z",
            "modified_time": "2026-10-11T13:48:35Z"
          }
        ]
      }
    },
    "related_cves": [],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 286054,
  "published_at": "2026-10-11T13:48:35+00:00"
}