GHSA-4jvx-93h3-f45h CVE-2026-42085 PYSEC-2026-2243

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

Medium PyPIRubyGems

Severity: 4.3 / 10; Medium · CVSS 3.1
Exploit chance (EPSS): 0.31%; Chance of exploitation in the next 30 days. Higher than 24.28% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-23 Relative Path Traversal
Fix: Available; 2 packages have a fixed version

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.

PoC

Navigate to any tool that enables “Save Configuration” option in left-hand drop-down menu (here Limits Monitor as an example)
Save a new config with path traversal name using “../” sequences to escape desired directory (up to 3 levels high)
Observe new files created in /plugins directory by inspecting docker container directly (openc3-COSMOS-cmd-tlm-api) or using Bucket Explorer (plugin_default)

Impact

Modifying the data of other plugins

Affected versions

PyPI

Package	Vulnerable	Fixed in
openc3	`< 6.10.5`	`6.10.5`

RubyGems

Package	Vulnerable	Fixed in
openc3	`< 6.10.5`	`6.10.5`
openc3	`>= 7.0.0.pre.rc1, < 7.0.0-rc3`	`7.0.0-rc3`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

openc3 PyPI → `6.10.5`

pip

pip install --upgrade "openc3>=6.10.5"

poetry

poetry add "openc3>=6.10.5"

uv

uv add "openc3>=6.10.5"

openc3 RubyGems → `6.10.5`

bundler

bundle update openc3 # Gemfile: gem "openc3", ">= 6.10.5"

Severity breakdown

CVSS 3.1 4.3

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

Attack vector: Network
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Weakness

CWE-23: Relative Path Traversal

The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory.

How to prevent it

Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. When validating filenames, use stringent allowlists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a list of allowable file extensions, which will help to avoid CWE-434. Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a denylist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would b
Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked. Use a built-in path canonicalization function (such as realpath() in C) that produces the canonical version of the pathname, which effectively removes ".." sequences and symbolic links (CWE-23, CWE-59). This includes: realpath() in C getCanonicalPath() in Java GetFullPath() in ASP.NET realpath() or abs_path() in Perl realpath() in PHP
Operation: Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].

References

Advisories

nvd.nist.gov/vuln/detail/CVE-2026-42085

Packages

github.com/OpenC3/cosmos

Timeline

Apr 22, 2026 Published
Oct 26, 2026 Last updated by the source
Nov 1, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-jjq7-m736-w977 OpenC3 COSMOS: Authenticated remote code execution via the user-writable config overlay (table definitions, cmd/tlm definitions, and script suites)	Critical	Also affects openc3
GHSA-vp3w-52v9-q57f OpenC3 COSMOS: Authenticated OS command injection via the `pypi_url` setting	High	Also affects openc3
GHSA-2wvh-87g2-89hr OpenC3 COSMOS: Permissions Bypass Provides User Access to Unassigned Administrative Actions via Script Runner Tool	High	Also affects openc3
GHSA-v529-vhwc-wfc5 OpenC3 COSMOS has SQL Injection in QuestDB Time-Series Database	Critical	Also affects openc3
GHSA-ffq5-qpvf-xq7x OpenC3 COSMOS is Vulnerable to Self-XSS Through the Command Sender	Medium	Also affects openc3
GHSA-wgx6-g857-jjf7 OpenC3 COSMOS: Hijacked session token can be used to reset password for persistence	High	Also affects openc3
GHSA-w757-4qv9-mghp openc3-api Vulnerable to Unauthenticated Remote Code Execution	Critical	Also affects openc3
GHSA-4xqv-47rm-37mm OpenC3 stores passwords in clear text (`GHSL-2024-129`)	Medium	Also affects openc3

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