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CVE-2026-42085 (openc3): OpenC3 COSMOS allows arbitrary writes to plugins directory via path-traversed config filenames

OpenC3 COSMOS allows arbitrary writes to plugins directory via path-traversed config filenames

Published: April 22, 2026

SECURITY IDENTIFIERS

GEM

openc3

SEVERITY

CVSS v3.x: 4.3 (Medium)

PATCHED VERSIONS

~> 6.10.5 >= 7.0.0-rc3

DESCRIPTION

Summary

OpenC3 COSMOS contains a design flaw in the save_tool_config() function that allows saving tool configuration files at arbitrary locations inside the shared /plugins directory tree by supplying crafted configuration filenames. Although the implementation sufficiently mitigates standard path traversal attacks, by canonicalizing filename to an absolute path, all plugins share this same root directory. That enables users to create arbitrary file structures and overwrite existing configuration files within the shared /plugins directory.

Details

In function save_tool_config() (local_mode.rb) responsible for saving user-supplied tool configuration, the desired saving directory is not sufficiently enforced, instead allowing writes inside entire OPENC3_LOCAL_MODE_PATH.

Impact

Modifying the data of other plugins.

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