Malicious code in semvver (PyPI)

{
  "id": "433101982d810313318c78cef005cffe78ef263e8b63a0bfb5cd4c9867a695cf",
  "url": "https://osv.dev/vulnerability/MAL-2026-18104",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Malicious code in semvver (PyPI)",
    "summary": "--- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (bbc16b0ced0bad1a33b912dfdb29cbaef211f30974d942991257d4e6b60a8ece) setup.py performs an install-time fetch-and-execute: it calls urllib.request.urlretrieve against https://c2-worker.crawlnet-claim.workers.dev/dl/pyupd, writes the response to a temporary path, and spawns it as a detached background process via subprocess.Popen with start_new_session=True. The fetch is unpinned and has no hash or signature verification, exceptions are swallowed, and the destination is a Cloudflare Workers subdomain unrelated to any PyPI publisher identity. The package has no other functionality — __init__.py is empty and the description is a generic 'utility helpers' string — so the install hook is the package's entire payload. The downloaded binary name 'pyupd' is a cover-story label; the behavior is a classic install-time dropper that grants whoever controls the Workers endpoint arbitrary code execution on the installer's host, running detached and persisting beyond the pip process. ## Source: kam193 (870775cad2a7f248b017394e8fbdb3470f6799de13d3ad278f1440b5b470c275) During installation, package downloads and executes malware. --- Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers. Campaign: 2026-10-semvver Reasons (based on the campaign): - Downloads and executes a remote executable. - malware - typosquatting",
    "evidence": "osv:MAL-2026-18104",
    "products": [
      {
        "name": {
          "value": "semvver",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "1.0.0",
            "evidence": "/affected/0/versions"
          }
        ]
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "MAL-2026-18104",
      "aliases": [
        "MAL-2026-18104"
      ],
      "affected": [
        {
          "package": {
            "name": "semvver",
            "purl": "pkg:pypi/semvver",
            "ecosystem": "PyPI"
          },
          "versions": [
            "1.0.0"
          ],
          "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/pypi/semvver/MAL-2026-18104.json",
            "indicators": {
              "evidence_files": [
                {
                  "path": "setup.py",
                  "tlsh": "58f0c992c617673582c2d231ee3204632ffb9603e783d8f0369c93946fce87a8124a09",
                  "sha256": "dcadfe8e0f4fcc578d613e8f9c0913edae241e61d39f2e5bac7425ab347148da"
                }
              ],
              "package_integrity": [
                {
                  "hashes": {
                    "md5": "ac69532606a46f0ae5a7ba85362c6ee9",
                    "sha256": "7cc51e37ad6c8bc62d3352b6f3976a9da8e2e5f6f77132c29603aca68ec17e9e",
                    "blake2b_256": "e40c725d4c4070b703f310d3ede05bec3c8e48aaf700fab9c1df23e9c2ecc073"
                  },
                  "filename": "semvver-1.0.0.tar.gz"
                }
              ]
            }
          }
        }
      ],
      "modified": "2026-10-22T23:45:03.532470872Z",
      "provider": "osv",
      "references": [
        "https://pypi.org/project/semvver/1.0.0/",
        "https://www.virustotal.com/gui/file/e6d96b5500b232bea67f6f9046cfbc22d29a515c42d2af9523a15ebe8a7c4ab7/",
        "https://bad-packages.kam193.eu/pypi/package/semvver"
      ],
      "provider_metadata": {
        "iocs": {
          "urls": [
            "https://c2-worker.crawlnet-claim.workers.dev/dl/pyupd"
          ],
          "domains": [
            "c2-worker.crawlnet-claim.workers.dev"
          ]
        },
        "malicious-packages-origins": [
          {
            "id": "IN-MAL-2026-021537",
            "sha256": "bbc16b0ced0bad1a33b912dfdb29cbaef211f30974d942991257d4e6b60a8ece",
            "source": "amazon-inspector",
            "versions": [
              "1.0.0"
            ],
            "import_time": "2026-10-20T18:22:19.910972281Z",
            "modified_time": "2026-10-20T18:20:39Z"
          },
          {
            "id": "pypi/2026-10-semvver/semvver",
            "sha256": "870775cad2a7f248b017394e8fbdb3470f6799de13d3ad278f1440b5b470c275",
            "source": "kam193",
            "versions": [
              "1.0.0"
            ],
            "import_time": "2026-10-20T19:15:26.421626699Z",
            "modified_time": "2026-10-20T18:27:10.366642Z"
          },
          {
            "id": "pypi/2026-10-semvver/semvver",
            "sha256": "54da4354cb1643cba5c4863a9b431e4a5d131045a6a4c839d911e949c6c9fb84",
            "source": "kam193",
            "versions": [
              "1.0.0"
            ],
            "import_time": "2026-10-22T23:38:53.991005308Z",
            "modified_time": "2026-10-20T18:27:10.366642Z"
          }
        ]
      }
    },
    "related_cves": [],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 410159,
  "published_at": "2026-10-20T18:20:39+00:00"
}