What’s Vulnerable › Vulnerabilities

CVE-2026-42085: OpenC3 COSMOS: Arbitrary write to plugins directory via path-traversed config filenames

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-05-04 · updated 2026-10-26
• Weakness: CWE-23

Description

OpenC3 COSMOS provides the functionality needed to send commands to and receive data from one or more embedded systems. Prior to versions 6.10.5 and 7.0.0-rc3, 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. This issue has been patched in versions 6.10.5 and 7.0.0-rc3.

Affected products

• OpenC3 cosmos: before 6.10.5; 7.0.0-rc1, 7.0.0-rc2 — fixed in 6.10.5

How to fix

Upgrade to a fixed version: OpenC3 cosmos 6.10.5. Check the vendor advisory for mitigations.

References

• https://github.com/OpenC3/cosmos/commit/9957a9fa460c0c0cf5cdbf6a5931bbdd025246a5
• https://github.com/OpenC3/cosmos/commit/e6efccbd148ba0e3361c5891027f2373aa140d42
• https://github.com/OpenC3/cosmos/releases/tag/v6.10.5
• https://github.com/OpenC3/cosmos/releases/tag/v7.0.0-rc3
• https://github.com/OpenC3/cosmos/security/advisories/GHSA-4jvx-93h3-f45h
• https://github.com/OpenC3/cosmos/security/advisories/GHSA-4jvx-93h3-f45h

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