Which versions of MailBee are malicious?

The following NuGet versions of MailBee are flagged malicious: 12.3.1, 12.3.2, 12.3.3, 12.3.4, 12.3.5. Treat any of these as compromised.

How do I remediate MailBee if I installed it?

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

If MailBee 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 MailBee part of a known attack campaign?

Yes — MailBee is associated with the RLMA-2024-03334 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 MailBee across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for MailBee (5 malicious versions).

Malicious package

MailBeeNuGet

MailBee is a confirmed malicious NuGet package (MAL-2024-4540) that executes malicious code on install (malicious versions 12.3.1, 12.3.2, 12.3.3…). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in MailBee (NuGet)

MAL-2024-4540

Immediate action

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

remove MailBee

Malicious versions

5 flagged

12.3.112.3.212.3.312.3.412.3.5

Indicators of compromise (SHA-256)

ae3e4dd84e70c213c84aff2757963d76fdc2ec112e7af44ae032cc70cd65c64a

Detection & response playbook

Malicious package

Find it
Search your lockfiles and build artifacts for MailBee (5 malicious versions).
If you installed it — respond
Remove MailBee 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 MailBee 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. MailBee on NuGet has been identified as a malicious package (versions 12.3.1, 12.3.2, 12.3.3, 12.3.4, 12.3.5 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

RLMA-2024-03334

Credits

ReversingLabs · finder

Detect & block this

O3 blocks MailBee-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

Explore

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