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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

EPSS

• CVE-2026-42085: 0.31% estimated exploitation activity in the next 30 days; percentile 24.32 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary OpenC3 COSMOS contains a design flaw in the savetoolconfig() 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 savetoolconfig() (localmode.rb) responsible for saving user-supplied tool configuration, the desired saving directory is not sufficiently enforced, instead allowing writes inside entire OPENC3LOCALMODEPATH. PoC 1. Navigate to any tool that enables “Save Configuration” option in left-hand drop-down menu (here Limits Monitor as an example) 2. Save a new config with path traversal name using “../” sequences to escape desired…

Published by the source

4 May 2026, 18:16 UTC

Last modified by the source

13 Jul 2026, 07:15 UTC

Source last checked

26 Oct 2026, 15:52 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-4jvx-93h3-f45h

2. Revision 1 · created · 24 Oct 2026

   Published from osv record PYSEC-2026-2243

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# Patch Next advisory brief: CVE-2026-42085

Advisory: OpenC3 COSMOS allows arbitrary writes to plugins directory via path-traversed config filenames
IDs: CVE-2026-42085, GHSA-4jvx-93h3-f45h
Record: https://patchnext.com/advisories/cve-2026-42085 (revision 2, source checked 26 Oct 2026, 15:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: openc3 6.10.5; openc3 7.0.0-rc3, 6.10.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI openc3: affected < 6.10.5; fixed in 6.10.5
- RubyGems openc3: affected < 6.10.5; >= 7.0.0.pre.rc1, < 7.0.0-rc3; fixed in 6.10.5, 7.0.0-rc3

## Suggested inspection (read-only)
- `python -m pip show openc3`: prints the installed version. Run with the environment that serves production active.
- RubyGems openc3: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on openc3.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/PYSEC-2026-2243 (OSV record PYSEC-2026-2243 lists affected ranges: PyPI openc3 >=0 <6.10.5 (fixed))
- Verified: https://github.com/advisories/GHSA-4jvx-93h3-f45h (GitHub-reviewed advisory GHSA-4jvx-93h3-f45h lists affected ranges: RubyGems openc3 >=0 =7.0.0.pre.rc1 <7.0.0-rc3)

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