---
title: "CVE-2026-77602: OpenC3 COSMOS: Authenticated remote code execution via the user-writable config overlay (table definitions, cmd/tlm definitions, and script suites)"
url: https://erroneo.us/security/cve/CVE-2026-77602/
description: "CVE-2026-77602 (openc3 (RubyGems)): OpenC3 COSMOS provides the functionality needed to send commands to and receive data from one or more embedded systems.…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-09-23
date_modified: 2026-09-29
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-77602"
kev: false
cvss: 9.9
epss: 0.00574
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-77602: OpenC3 COSMOS: Authenticated remote code execution via the user-writable config overlay (table definitions, cmd/tlm definitions, and script suites)

**Signal:** Critical, preconditions apply. Severe if exploited, but exploitation needs conditions that may not apply to you. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.6% , percentile 47: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 47% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Needs an account (low (any account)). Exposure depends on who can log in.
- Only applies if your dependency tree includes openc3 (RubyGems) >= 5.1.0, <= 7.2.1, fixed in 7.3.0 . Check your lockfile, including transitive dependencies.

## What it is

OpenC3 COSMOS provides the functionality needed to send commands to and receive data from one or more embedded systems. From 5.1.0 until 7.3.0, authenticated non-administrator users can write content under targetsmodified/ that is later executed by multiple configuration paths below the intended code-execution privilege tier. Table and command or telemetry definitions are processed through ConfigParser, PacketConfig, GENERICREADCONVERSION, or GENERICWRITECONVERSION, allowing ERB rendering or Ruby and Python evaluation, while openc3-cosmos-script-runner-api/scripts/runsuiteanalysis.rb executes suite procedure files through require. Storage uploads, screen saves, and script creation can place content in the overlay, and triggering table processing, a cmd/tlm reload, or suite analysis executes the content in cmd-tlm-api, decom microservices, or Script Runner with access to internal credentials and data. This issue is fixed in version 7.3.0.

## Affected packages

- RubyGems `openc3` >= 5.1.0, <= 7.2.1 → fixed: 7.3.0

## Affected products (CVE record)

- OpenC3 cosmos: >= 5.1.0, < 7.3.0

## Severity

- GitHub_M CVSS 3.1: 9.9 `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.9 `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.57% probability of exploitation activity in the next 30 days; percentile 47.

## Sources

- [GitHub Advisory GHSA-jjq7-m736-w977](https://github.com/advisories/GHSA-jjq7-m736-w977)
- [CVE.org record CVE-2026-77602](https://www.cve.org/CVERecord?id=CVE-2026-77602)
- [NVD entry CVE-2026-77602](https://nvd.nist.gov/vuln/detail/CVE-2026-77602)
- [github.com](https://github.com/OpenC3/cosmos/security/advisories/GHSA-jjq7-m736-w977)
- [github.com](https://github.com/OpenC3/cosmos/pull/3488)
- [github.com](https://github.com/OpenC3/cosmos/commit/71943352a28128ef3e7e894319d97a656b5cd4f2)
- [github.com](https://github.com/OpenC3/cosmos/commit/7a1538a4626f82c0d1540fcaa27ffdcbbd71ff81)

---
Source page: https://erroneo.us/security/cve/CVE-2026-77602/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt