NIST deprecates RSA-2048 from 2030. Find every one of them before attackers do.
Malicious package

pylogfmtPyPI

Advisory published Updated

pylogfmt is a confirmed malicious PyPI package (MAL-2026-4231) that steals credentials and exfiltrates sensitive data (malicious version 0.1.0). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in pylogfmt (PyPI)

MAL-2026-4231
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
pip uninstall pylogfmt

What this malware does

On import pylogfmt, the package's init.py spawns a detached background subprocess (subprocess.Popen([sys.executable, '_check.py'], stdout=DEVNULL, stderr=DEVNULL)) that runs an infinite loop POSTing the package install path to https://pypkg.dev/project/pylogfmt/json every 60 seconds with TLS verification explicitly disabled. The HTTP response body is base64-decoded and dispatched to a worker thread (threading.Thread(target=check, args=(package_list.decode(),))), which is the canonical remote-payload-dispatcher shape — the operator controls returned bytes and the client decodes and feeds them into a handler. The destination domain pypkg.dev is a lookalike of pypi.org/pypa with no relation to the package's declared logging-library purpose. Output suppression (DEVNULL on both streams), undocumented behavior (README advertises only a logging helper), TLS bypass, and lookalike C2 destination together are unambiguous attack signals. Any consumer that imports pylogfmt as a library leaks their install path to attacker infrastructure on a 60-second polling interval and is one server-side change away from arbitrary remote code execution.

Package silently executes remote code during import.

Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers.

Campaign: 2026-05-lognest

Reasons (based on the campaign):

  • Downloads and executes a remote malicious script.

Malicious versions

1 flagged
0.1.0

Indicators of compromise (SHA-256)

ba18f7e82fa8d07985ef44f6ce5a8d4b7759f2e348b6ba073bba4dd463740d8e
34bc39125496330ed9b38f1f6d7f06db7e150d83144f9d7e1e04552112851c4a

Detection & response playbook

Credential / info stealer
  1. Find it

    Search your lockfiles and build artifacts for pylogfmt (version 0.1.0).

  2. If you installed it — respond

    pylogfmt 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.

  3. Did it already run?

    If pylogfmt 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

No. pylogfmt on PyPI has been identified as a malicious package (version 0.1.0 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

2026-05-lognestIN-MAL-2026-004107

References

Credits

  • Amazon Inspector · finder
  • Kamil Mańkowski (kam193) · reporter

Detect & block this

O3 blocks pylogfmt-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.

Explore

pylogfmt (PyPI) malicious package — MAL-2026-4231 | O3 Security