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CVE-2026-77394— OpenC3 COSMOS: Stored, cross-user XSS via Telemetry screen BUTTON widget

Quick assessment

Affected
OpenC3 cosmos
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

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 BU

CVSS 7.6 · High

Possible ATT&CK Techniques 2 AI

T1059.007 · JavaScript T1190.001

Affected Version Matrix 1

VendorProduct Version RangeStatus
OpenC3 cosmos >= 5.0.6, < 7.3.0 affected
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I. Basic Information for CVE-2026-77394

Vulnerability Information

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Vulnerability Title
OpenC3 COSMOS: Stored, cross-user XSS via Telemetry screen BUTTON widget
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
OpenC3 cosmos >= 5.0.6, < 7.3.0 -

II. Public POCs for CVE-2026-77394

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III. Intelligence Information for CVE-2026-77394

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Other References for CVE-2026-77394 (4)

Same Patch Batch · OpenC3 · 2026-09-23 · 3 CVEs total

CVE-2026-77602 9.9 CRITICAL OpenC3 COSMOS: Authenticated remote code execution via the user-writable config overlay (t
CVE-2026-77601 8.8 HIGH OpenC3 COSMOS: Authenticated OS command injection via the `pypi_url` setting

IV. Related Vulnerabilities

Same product: cosmos
Same vendor: OpenC3
Same weakness: CWE-79

V. Comments for CVE-2026-77394

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