Executive brief
Penelope Shell Handler, a tool used by security professionals for managing remote sessions during authorized testing, contains a vulnerability in how it handles file downloads. If an operator attempts to download files from a compromised or malicious remote system, that system can send a specially crafted archive that writes files to unauthorized locations on the operator's computer. This could allow an attacker to overwrite configuration files or plant malicious code that executes the next time the tool is started, potentially leading to a full compromise of the operator's workstation.
Technical details
A path traversal vulnerability exists in the Unix `download()` implementation within `penelope.py`. The application uses `tar.extractall()` on archives received from remote sessions without validating the paths of the archive members. An attacker controlling a remote session can return a crafted tar archive containing members with traversal sequences (e.g., `../`). This allows the attacker to write files outside the intended `downloads` directory, specifically targeting `~/.penelope/peneloperc`. Because Penelope executes the contents of `peneloperc` via `exec()` during startup or reload, this provides a direct path to arbitrary code execution on the operator's machine. The issue is fixed in version 0.20.0 by implementing explicit validation of archive paths.
Affected products
- brightio penelope-shell-handler < 0.20.0
Timeline
- 2026-05-30: patched: Version 0.20.0 released
- 2026-06-08: advisory: GitHub Security Advisory published
- 2026-07-29: disclosed: NVD publication date