CVE-2026-42085 OpenC3 COSMOS: Arbitrary write to plugins directory via path-traversed config filenames
Attackers can overwrite configuration files in the shared plugins directory by crafting filenames, potentially compromising system integrity.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42085?
CVE-2026-42085 is a medium-severity path traversal vulnerability in OpenC3 cosmos, published on 4 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-23
Which versions are affected by CVE-2026-42085?
5 open source packages ship an affected version, including openc3. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
openc3 PyPI | All versions | 6.10.5 |
openc3 RubyGems | All versions | 6.10.5 |
openc3 RubyGems | All versions | 6.10.5 |
openc3 RubyGems | From 7.0.0.pre.rc1 | 7.0.0-rc3 |
openc3 RubyGems | From 7.0.0.pre.rc1 | 7.0.0-rc3 |
Products include Openc3 Cosmos.
How do I fix CVE-2026-42085?
Upgrade openc3 to a fixed version for your release line: 6.10.5 or 7.0.0-rc3.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-42085 being exploited?
There is no known exploitation of CVE-2026-42085 in the wild and no public exploit code.
Other vulnerabilities in OpenC3 cosmos
Sources
Also known as GHSA-4jvx-93h3-f45h, PYSEC-2026-2243.