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CriticalPublished 27 Mar 20261 package · 2 versions

Telnyx Python SDK hides credential stealer in WAV-file steganography

Summary

TeamPCP published malicious telnyx 4.87.1 and 4.87.2 to PyPI on 27 March 2026 (~670k monthly downloads). Trojanised _client.py downloads steganographic payloads disguised as .wav files over plaintext HTTP, extracts the credential stealer, and persists. Windows variant drops msbuild.exe to the Startup folder; Linux variant uses a user-level systemd service. AES-256-CBC + RSA-4096 envelope for exfil.

maintainer-takeovercredential-theftobfuscationinfostealer
Threat actor
TeamPCP
Detected by
JFrog
Ecosystems
PyPI
Packages tracked
1

What happened

On 27 March 2026 the threat group TeamPCP published two trojanised releases of telnyx (4.87.1 and 4.87.2) - the official Python SDK for the Telnyx voice/SMS platform with roughly 670k monthly downloads. The malicious code lives inside telnyx/_client.py and runs the moment any consumer imports the SDK.

The loader pulls steganographic payloads from 83.142.209.203:8080/hangup.wav and /ringtone.wav over plaintext HTTP. Audio frames hide a base64 + XOR-encoded blob that decrypts into a credential stealer. Exfiltration uses an AES-256-CBC payload wrapped in an RSA-4096 envelope, tagged with the header X-Filename: tpcp.tar.gz.

Persistence is OS-specific:

  • Windows drops msbuild.exe into %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup\ and uses an .lock companion file.
  • Linux installs a user-level audiomon.service systemd unit under ~/.config/systemd/user/ backed by ~/.config/audiomon/.

This is TeamPCP's second high-impact campaign in a week - JFrog tied the same actor to the earlier litellm PyPI compromise. PyPI quarantined both versions, but any environment that resolved telnyx>=4.87.1 during the live window should treat developer credentials and host metadata as compromised.

Affected packages (1)

These are usually pulled in as transitive dependencies rather than installed directly. Check your whole tree at once - it runs in your browser and nothing is uploaded.

Check requirements.txt

Impact

  • Persistent Windows execution as msbuild.exe in Startup
  • Linux user-level systemd persistence (audiomon.service)
  • Credential and host-metadata exfiltration to attacker C2
  • Targets developers integrating with Telnyx voice/SMS APIs

What to do

  1. 1Downgrade to telnyx 4.87.0 or earlier
  2. 2Delete %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup\msbuild.exe
  3. 3Remove ~/.config/audiomon/ and ~/.config/systemd/user/audiomon.service
  4. 4Block 83.142.209.203:8080 and the /hangup.wav, /ringtone.wav URIs

References

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pypi-2026-03-27-telnyx-teampcp