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🛡️ CVE-2026-42085 — cosmos

🟡 CVSS 4.3 — Medium ⚠️ Exploit Public CWE-23 NVD
4.3
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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

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](https://github.com/OpenC3/cosmos/blob/397abec0d57972881a2e8dc10902d0dce9c27f42/openc3/lib/openc3/utilities/local_mode.rb#L452)) responsible for saving user-supplied tool configuration, the desired saving directory is not sufficiently enforced, instead allowing writes inside entire OPENC3_LOCAL_MODE_PATH.

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 directory (up to 3 levels high)

3. Observe new files created in /plugins directory by inspecting docker container directly (openc3-COSMOS-cmd-tlm-api) or using Bucket Explorer (plugin_default)

<img width="811" height="584" alt="image" src="https://github.com/user-attachments/assets/015a59b4-8b18-4801-aef0-df4831d5c1c3" />

<img width="720" height="664" alt="image" src="https://github.com/user-attachments/assets/8ca4a5b7-ee45-4c3b-99f6-f41f974a74a7" />

Impact

Modifying the data of other plugins

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity low, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: Low — limited, and the attacker does not choose what is affected.
  • Availability impact: None.

Weakness class

CVE-2026-42085 is classified as CWE-23: Relative Path Traversal. Relative path sequences in user input are not neutralised, so requests can climb out of the intended directory.

Affected software

CVE-2026-42085 is recorded against 2 packages.

  • cosmos
  • openc3 (fixed in 6.10.5)

Timeline and source

Published on 4 May 2026 and last revised on 17 June 2026. A public exploit is known to exist, which raises the urgency of patching considerably. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
github.com
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Other advisories for this package

cosmos has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-23: Relative Path Traversal) in other software:

Details

Severity MEDIUM
CVSS Score 4.3
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
CWE CWE-23
Public Exploit ⚠️ Yes
Source NVD
Published 2026-05-04
Updated 2026-08-20
Modified 2026-06-17

Affected Packages

Software From version Fixed in
cosmos — —
openc3 — 6.10.5

Similar Threats

Exploit Protection

Are you running cosmos?

CVE-2026-42085 carries CVSS 4.3 Medium rating and a public exploit already exists. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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