Which versions of pkg-fallback are malicious?

The following PyPI versions of pkg-fallback are flagged malicious: 1.1.0. Treat any of these as compromised.

How do I remediate pkg-fallback if I installed it?

pkg-fallback 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.

I already installed pkg-fallback — how do I know if it already compromised me?

If pkg-fallback 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.

Is pkg-fallback part of a known attack campaign?

Yes — pkg-fallback is associated with the IN-MAL-2026-007697, GENERIC-beacon-dependency-confusion campaign. Packages in the same campaign often share infrastructure and payloads, so check whether any related packages are also in your dependency tree.

How do I find pkg-fallback across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for pkg-fallback (version 1.1.0).

Malicious package

pkg-fallbackPyPI

Advisory published Jun 28, 2026Updated Jun 28, 2026

pkg-fallback is a confirmed malicious PyPI package (MAL-2026-6557) that steals credentials and exfiltrates sensitive data (malicious version 1.1.0). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in pkg-fallback (PyPI)

MAL-2026-6557

Immediate action

Remove the package, then rotate any secrets the build/runtime could reach.

pip uninstall pkg-fallback

What this malware does

setup.py performs an unconditional urllib.request.urlopen() at install time to a hardcoded plaintext bare-IP endpoint http://157.254.194.200:8080/dependency-payload-1.0.0.tar.gz, with exceptions silently swallowed. This fires automatically during pip install (build/setup phase), confirming code execution on the installer's machine and disclosing the installer's network identity to attacker-controlled infrastructure. The distribution is published as 'pkg-fallback' but ships an unrelated 'string_kit' module described as 'string-kit' in README/PKG-INFO; the name/module divergence together with the install-time bare-IP beacon and the attacker-suggestive payload filename ('dependency-payload') is consistent with a dependency-confusion staging/enumeration package rather than a genuine utility.

Package exploits dependency confusion. A beacon request is used to report usage back, but no additional information are exfiltrated.

Category: PROBABLY_PENTEST - Packages looking like typical pentest packages, but also anything that looks like testing, exploring pre-prepared kits, research & co, with clearly low-harm possibilities.

Campaign: GENERIC-beacon-dependency-confusion

Reasons (based on the campaign):

typosquatting
dependency-confusion

Malicious versions

1 flagged

1.1.0

Indicators of compromise (SHA-256)

7f4ccaa9f059318782cd3b811f5bd6ea926e267e4b05dc4971d6acc6687d5d4f

4563c95d80446cbc0c815185ab9b3649b048c82a33b2d662523ce4760dbc6856

Detection & response playbook

Credential / info stealer

Find it
Search your lockfiles and build artifacts for pkg-fallback (version 1.1.0).
If you installed it — respond
pkg-fallback 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 pkg-fallback 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. pkg-fallback on PyPI has been identified as a malicious package (version 1.1.0 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-007697GENERIC-beacon-dependency-confusion

References

Credits

Amazon Inspector · finder
Kamil Mańkowski (kam193) · reporter

Detect & block this

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

Malware detection Runtime egress monitoring

Explore

All malware advisories How O3 detects malware Vulnerability database