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 ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.

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?

Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for pkg-fallback (version 1.1.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging pkg-fallback across your stack and pipelines.

Malicious package

pkg-fallbackPyPI

Malicious code in pkg-fallback (PyPI) Remove it immediately and rotate any exposed credentials.

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
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for pkg-fallback (version 1.1.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging pkg-fallback across your stack and pipelines.
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 ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks pkg-fallback before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.

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