semveerPyPI
Advisory published Updated
semveer is a confirmed malicious PyPI package (MAL-2026-18102) that steals credentials and exfiltrates sensitive data (malicious version 1.0.0). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in semveer (PyPI)
What this malware does
The sdist for 'semveer' ships an inert module (semveer/init.py contains only a version stub) and places all runtime behavior inside setup.py's install hook. On pip install, setup.py calls urllib.request.urlretrieve against https://c2-worker.crawlnet-claim.workers.dev/dl/pyupd, writes the opaque payload to a temporary file, and launches it via subprocess.Popen with start_new_session=True as a detached process. The fetch is wrapped in a bare try/except that suppresses errors, there is no hash or signature verification, the version is not pinned, and the destination host is unrelated to any declared publisher or project homepage. The package name is a one-character edit of the widely used 'semver' name, consistent with a typosquat lure whose only purpose is to trigger the install-time dropper.
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
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Credential / info stealerFind it
Search your lockfiles and build artifacts for semveer (version 1.0.0).
If you installed it — respond
semveer is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.
Did it already run?
If semveer was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
- Kamil Mańkowski (kam193) · reporter
Detect & block this
O3 blocks semveer-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.