Malicious code in multichain-rpc (RubyGems)

{
  "id": "a19ad9b4a83b61d97b2eb482dd5f53ccf9c4c69e769d3ea7b44a8b1eb51e774c",
  "url": "https://osv.dev/vulnerability/MAL-2026-17791",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Malicious code in multichain-rpc (RubyGems)",
    "summary": "--- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (b5765482ebcff5ac393edb3ce06164e7c697a00aa7e32c92b1272dc20184b424) The gem's extconf.rb, executed automatically by `gem install` as a native-extension build step, base64-decodes a Ruby payload and runs it via `eval` inside a double-forked, stdio-detached background process. The payload opens a TCP socket to the hardcoded host 45.138.12.177 on port 8089 and bridges it to `/bin/sh`, giving the remote operator an interactive shell on the installer's machine. Execution is gated by developer-host heuristics (presence of ~/.ssh, ~/.gitconfig, ~/.npmrc, ~/.gem/credentials, ~/.bundle, uptime > 1800s) and explicit anti-analysis checks that skip CI, ephemeral, generated-user, and sandbox environments, with a 20-40 minute delay before firing. The rest of the gem is cover: lib/multichain_rpc.rb exports only stub methods (`build_id` returning 'ok', `healthy?` returning true), the README advertises an unrelated name (`bitcoin-rpc-lite`), and extconf.rb declares a native extension (`create_makefile('bitcoin_rpc_lite_native')`) but ships no C sources, so the file's sole purpose is to run the embedded payload. Installing the gem on a developer workstation yields a full-host remote shell to the attacker.",
    "evidence": "osv:MAL-2026-17791",
    "products": [
      {
        "name": {
          "value": "multichain-rpc",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "0.9.1",
            "evidence": "/affected/0/versions"
          }
        ]
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "MAL-2026-17791",
      "aliases": [
        "MAL-2026-17791"
      ],
      "affected": [
        {
          "package": {
            "name": "multichain-rpc",
            "purl": "pkg:gem/multichain-rpc",
            "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/multichain-rpc/MAL-2026-17791.json",
            "indicators": {
              "evidence_files": [
                {
                  "path": "ext/multichain_rpc/extconf.rb",
                  "tlsh": "9751775acf8359e55aa1c0c045798012faa3ab0a50646875f3ee0868ff59b26c0f12fe",
                  "sha256": "10218e975f54a4f11fe3954e1b584a5f05054003bf5773c3c2b8cceaa74ba763"
                },
                {
                  "path": "metadata.yaml",
                  "tlsh": "b511a0c0ad82fa36f051e2ee68602343b363d50cfe562905d9b78195d3c61afa647431",
                  "sha256": "8834de8777f59908dd519a9c0d89a23d0e15fabbaa813a596be502eba92321b7"
                }
              ]
            }
          }
        }
      ],
      "modified": "2026-10-11T14:30:06.028894095Z",
      "provider": "osv",
      "references": [
        "https://rubygems.org/gems/multichain-rpc/versions/0.9.1"
      ],
      "provider_metadata": {
        "malicious-packages-origins": [
          {
            "id": "IN-MAL-2026-021369",
            "sha256": "b5765482ebcff5ac393edb3ce06164e7c697a00aa7e32c92b1272dc20184b424",
            "source": "amazon-inspector",
            "versions": [
              "0.9.1"
            ],
            "import_time": "2026-10-11T14:17:59.895779205Z",
            "modified_time": "2026-10-11T13:48:54Z"
          }
        ]
      }
    },
    "related_cves": [],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 286033,
  "published_at": "2026-10-11T13:48:54+00:00"
}