{"id":"MAL-2026-18104","title":"Malicious code in semvver (PyPI)","summary":"Malicious code in semvver (PyPI)","severity":"critical","exploited":true,"vendor":"semvver","product":"semvver","ecosystem":"pip","affected":["semvver"],"published":"2026-10-20","updated":"2026-10-20","sourceUpdated":"2026-10-20T19:30:07.604250075Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/MAL-2026-18104","references":[{"url":"https://pypi.org/project/semvver/1.0.0/"},{"url":"https://www.virustotal.com/gui/file/e6d96b5500b232bea67f6f9046cfbc22d29a515c42d2af9523a15ebe8a7c4ab7/"},{"url":"https://bad-packages.kam193.eu/pypi/package/semvver"}],"tags":["osv","pip","malware"],"ingestedAt":"2026-10-21T11:54:42.742Z","slug":"MAL-2026-18104","body":"## Overview\n\n\n---\n_-= Per source details. Do not edit below this line.=-_\n\n## Source: amazon-inspector (bbc16b0ced0bad1a33b912dfdb29cbaef211f30974d942991257d4e6b60a8ece)\nsetup.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.\n\n## Source: kam193 (870775cad2a7f248b017394e8fbdb3470f6799de13d3ad278f1440b5b470c275)\nDuring installation, package downloads and executes malware.\n\n\n---\n\nCategory: MALICIOUS - The campaign has clearly malicious intent, like infostealers.\n\n\nCampaign: 2026-10-semvver\n\n\nReasons (based on the campaign):\n\n\n - Downloads and executes a remote executable.\n\n\n - malware\n\n\n - typosquatting\n\n\n## Affected packages\n\n- `semvver`\n\n## Remediation\n\nRefer to the advisory for the patched release.","depth":"abyssal","depthScore":70,"depthScoreParts":{"impact":52.3,"likelihood":0,"exploitation":18,"ransomware":0},"changes":[]}