CVE-2026-77394

OpenC3 COSMOS: Stored, cross-user XSS via Telemetry screen BUTTON widget

Published Sep 23, 2026 CVSS 3.1 · 7.6 High EPSS < 1% KEV · Not listed
Description
OpenC3 COSMOS provides the functionality needed to send commands to and receive data from one or more embedded systems. From 5.0.6 until 7.3.0, an authenticated actor with system_set permission can store a shared screen through POST /openc3-api/screen whose BUTTON widget action is evaluated by openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/ButtonWidget.vue in another operator's browser session when the button is activated. The stored script runs in the COSMOS origin and can read localStorage.openc3Token, allowing theft of the victim's bearer token, account takeover, and actions with the victim's privileges. The permissive content security policy contributes to execution but is not the primary root cause. This issue is fixed in version 7.3.0.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-gvf2-2rh5-mpgf OpenC3 COSMOS: Stored, cross-user XSS via Telemetry screen BUTTON widget
History
Type Values Removed Values Added
First Time appeared Openc3
Openc3 cosmos
Vendors & Products Openc3
Openc3 cosmos
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description OpenC3 COSMOS provides the functionality needed to send commands to and receive data from one or more embedded systems. From 5.0.6 until 7.3.0, an authenticated actor with system_set permission can store a shared screen through POST /openc3-api/screen whose BUTTON widget action is evaluated by openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/ButtonWidget.vue in another operator's browser session when the button is activated. The stored script runs in the COSMOS origin and can read localStorage.openc3Token, allowing theft of the victim's bearer token, account takeover, and actions with the victim's privileges. The permissive content security policy contributes to execution but is not the primary root cause. This issue is fixed in version 7.3.0.
Title OpenC3 COSMOS: Stored, cross-user XSS via Telemetry screen BUTTON widget
Weaknesses CWE-79
References
Metrics cvssV3_1

{'score': 7.6, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Sep 23, 2026, 7:28 PM
Reserved
Aug 20, 2026, 7:55 PM
Status
Deferred
Published
Sep 23, 2026, 7:19 PM
Modified
Sep 23, 2026, 8:17 PM