Which versions of biuundler are malicious?

The following RubyGems versions of biuundler are flagged malicious: 1.0.0, 1.0.63251. Treat any of these as compromised.

How do I remediate biuundler if I installed it?

Remove biuundler from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.

I already installed biuundler — how do I know if it already compromised me?

If biuundler 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 biuundler part of a known attack campaign?

Yes — biuundler is associated with the RLMA-2026-07377 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 biuundler across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for biuundler (2 malicious versions).

Malicious package

biuundlerRubyGems

Advisory published Sep 22, 2026Updated Sep 24, 2026

biuundler is a confirmed malicious RubyGems package (MAL-2026-16713) that executes malicious code on install (malicious versions 1.0.0, 1.0.63251). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in biuundler (RubyGems)

MAL-2026-16713

Immediate action

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

gem uninstall biuundler

Malicious versions

2 flagged

1.0.01.0.63251

Indicators of compromise (SHA-256)

fc5a049e5460dcb83fe87033c949ce6cbc24573d792078189e2be371f419c710

Detection & response playbook

Malicious package

Find it
Search your lockfiles and build artifacts for biuundler (2 malicious versions).
If you installed it — respond
Remove biuundler from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.
Did it already run?
If biuundler 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. biuundler on RubyGems has been identified as a malicious package (versions 1.0.0, 1.0.63251 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

RLMA-2026-07377

Credits

ReversingLabs · finder

Detect & block this

O3 blocks biuundler-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.

Malware detection Runtime egress monitoring

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