semverr

GHSA-j4xr-hh3p-8vmm

Malicious code in semverr (PyPI)

Details

**Severity:** Critical

**Affected versions:** `= 1.0.0`

## Source: amazon-inspector (110e0a64dd80654ca98caa5e291499d158a39eb66c1d35efe896a42095c85118)
semverr is a near-empty package (a one-line __version__) whose name resembles the popular semver library. Its setup.py runs at install time (invoked by pip during `pip install`) and calls urllib.request.urlretrieve to fetch an opaque binary from https://c2-worker.crawlnet-claim.workers.dev/dl/pyupd, writes it to a PID-suffixed path in the system temp directory, and launches it via subprocess.Popen with start_new_session=True and stdout/stderr redirected to DEVNULL so the detached child survives the install and runs silently. The fetch is unpinned, unverified (no hash or signature check), and directed at an anonymous Cloudflare Workers host unrelated to any declared publisher. Exceptions in the fetch/exec path are swallowed so install still appears to succeed. The package has no other functionality.

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Credit: [OpenSSF](https://github.com/ossf/malicious-packages) ([source](https://github.com/ossf/malicious-packages/blob/e29c7e37b0612ba04bf703b601e4f2a2ac4a98de/osv/malicious/pypi/semverr/MAL-2026-18103.json))

**References:**
- https://github.com/ossf/malicious-packages/blob/e29c7e37b0612ba04bf703b601e4f2a2ac4a98de/osv/malicious/pypi/semverr/MAL-2026-18103.json
- https://pypi.org/project/semverr/1.0.0
- https://bad-packages.kam193.eu/pypi/package/semverr
- https://github.com/ossf/malicious-packages/blob/5b75048f63715357959b2e2456ba15740497bba3/osv/malicious/pypi/semverr/MAL-2026-18103.json
- https://www.virustotal.com/gui/file/e6d96b5500b232bea67f6f9046cfbc22d29a515c42d2af9523a15ebe8a7c4ab7
- https://github.com/ossf/malicious-packages/blob/65a30c2bd1748889a5fb95a96da4a49b781c4b60/osv/malicious/pypi/semverr/MAL-2026-18103.json
- https://github.com/advisories/GHSA-j4xr-hh3p-8vmm

Compromised versions (1)

= 1.0.0

Any computer that installed or ran a compromised version should be considered fully compromised. Rotate every secret on that machine from a clean environment.