GitHub Advisoryadvisory · RubyGems, PyPI
GHSA-ffq5-qpvf-xq7x OpenC3 COSMOS is Vulnerable to Self-XSS Through the Command Sender
MEDIUM
Official page ↗
- Aliases
- CVE-2026-42086
- Ecosystem
- RubyGems, PyPI
- Packages
- openc3
- Severity
- Moderate
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N
- Weaknesses
- CWE-79
- Reviewed
- 2026-04-22
Affected packages
• RubyGems openc3: < 7.0.0 → fixed in 7.0.0
• PyPI openc3: < 7.0.0 → fixed in 7.0.0
Description
Summary
The Command Sender UI uses an unsafe `eval()` function on array-like command parameters, which allows a user-supplied payload to execute in the browser when sending a command. This creates a self-XSS risk because an attacker can trigger their own script execution in the victim’s session, if allowed to influence the array parameter input, for example via phishing. If successful, an attacker may read or modify data in the authenticated browser context, including session tokens in local storage.
Details
The unsafe `eval()` usage on user-supplied ARRAY parameters happens in `convertToValue` method in CommandSender.vue
PoC
1. Using a drop-down form, choose any command that supports ARRAY parameters,
2. Inside square brackets “[…]” place a JavaScript code to be executed
3. Send command to CmdTlmServer using dedicated “Send” button
4. Observe JavaScript code being executed in the current browser session context
Below example uses `INST ARYCMD` to execute simple JavaScript code snippet `alert(“XSS”)`.
Impact
Local JavaScript execution in the user's browser
Related
Alias · CVE (1)
- CVE-2026-42086 OpenC3 COSMOS provides the functionality needed to send commands to and receive data from one or more embedded systems. vulnerability
Weakness · CWE (1)
- CWE-79 Improper Neutralization of Input During Web Page Generation weakness
References
- https://github.com/OpenC3/cosmos/security/advisories/GHSA-ffq5-qpvf-xq7x web
- https://nvd.nist.gov/vuln/detail/CVE-2026-42086 advisory
- https://github.com/OpenC3/cosmos package
- https://github.com/pypa/advisory-database/tree/main/vulns/openc3/PYSEC-2026-105.yaml web
- https://github.com/rubysec/ruby-advisory-db/blob/master/gems/openc3/CVE-2026-42086.yml web