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Fencer Vulns
medium 4.3

CVE-2026-42085 json

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

published 2026-04-22 6 mo ago modified 2026-10-26 13 d ago also EUVD-2026-27059 , GHSA-4jvx-93h3-f45h , PYSEC-2026-2243

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits
0
none known

Summary

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.

Patch / fix

  • rubygems openc3 6.10.5, 7.0.0-rc3
  • pypi openc3 6.10.5
  • openc3 cosmos 6.10.5, 7.0.0-rc3

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.31% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/OpenC3/cosmos/security/advisories/GHSA-4jvx-93h3-f45h referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
GitHub 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
OSV 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
rubygems openc3
<6.10.5
>=7.0.0.pre.rc1, <7.0.0-rc3
6.10.5
7.0.0-rc3
pypi openc3
<6.10.5
6.10.5

Affected products

  • OpenC3 cosmos

Classification

Weakness
  • CWE-23 Relative Path Traversal

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.