Which versions of fosscallamb are malicious?

The following RubyGems versions of fosscallamb are flagged malicious: 0.0.1. Treat any of these as compromised.

How do I remediate fosscallamb if I installed it?

Remove fosscallamb 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 fosscallamb — how do I know if it already compromised me?

If fosscallamb 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 fosscallamb part of a known attack campaign?

Yes — fosscallamb is associated with the RLMA-2026-02340, RLUA-2026-08117 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 fosscallamb across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for fosscallamb (version 0.0.1).

Malicious package

fosscallambRubyGems

Advisory published Jul 7, 2026Updated Sep 24, 2026

fosscallamb is a confirmed malicious RubyGems package (MAL-2026-7689) that executes malicious code on install (malicious version 0.0.1). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in fosscallamb (RubyGems)

MAL-2026-7689

Immediate action

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

gem uninstall fosscallamb

Malicious versions

1 flagged

0.0.1

Indicators of compromise (SHA-256)

c5d48b40cdb468e8f92334c886ef8491b3e28b39b1cafe5875098cf99e5ed280

7d6fe92386d48291c8f486237437611fb3ac6f05ccb9c3c9081a53038127f9fe

Detection & response playbook

Malicious package

Find it
Search your lockfiles and build artifacts for fosscallamb (version 0.0.1).
If you installed it — respond
Remove fosscallamb 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 fosscallamb 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. fosscallamb on RubyGems has been identified as a malicious package (version 0.0.1 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

RLMA-2026-02340RLUA-2026-08117

References

github.com

Credits

ReversingLabs · finder

Detect & block this

O3 blocks fosscallamb-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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