---
id: MAL-2026-18101
title: Malicious code in semmver (PyPI)
summary: Malicious code in semmver (PyPI)
severity: critical
exploited: true
vendor: semmver
product: semmver
ecosystem: pip
affected:
  - semmver
published: '2026-10-20'
updated: '2026-10-20'
sourceUpdated: '2026-10-20T19:30:08.005669568Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/MAL-2026-18101'
references:
  - url: 'https://pypi.org/project/semmver/1.0.0/'
  - url: >-
      https://www.virustotal.com/gui/file/e6d96b5500b232bea67f6f9046cfbc22d29a515c42d2af9523a15ebe8a7c4ab7/
  - url: 'https://bad-packages.kam193.eu/pypi/package/semmver'
tags:
  - osv
  - pip
  - malware
ingestedAt: '2026-10-21T11:54:42.741Z'
---

## Overview


---
_-= Per source details. Do not edit below this line.=-_

## Source: amazon-inspector (8de323d5976a26f2d9540680d1706a53bcb3ca743409821e83f7a2f1b60e8594)
The package is a typosquat-style empty stub (semmver/__init__.py contains only __version__ = '1.0.0') whose only functional code is in setup.py. At pip install time, setup.py calls urllib.request.urlretrieve to download an opaque, unpinned binary from https://c2-worker.crawlnet-claim.workers.dev/dl/pyupd, writes it to a temporary path, and launches it via subprocess.Popen with start_new_session=True and stdout/stderr suppressed, detaching it from the installer process. There is no hash or signature verification, no pinning, and the destination host is unrelated to any legitimate utility purpose; the subdomain is self-labeled 'c2-worker'. Installing this package executes attacker-controlled code on the installer's machine.

## Source: kam193 (7b4ffebc6fe59fc1db7154c0a7ed9e6788d6a27ccea81fe1f4df432578b2c4d6)
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


## Affected packages

- `semmver`

## Remediation

Refer to the advisory for the patched release.