CVE-2026-77394

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.

Overview

State: PUBLISHED
Assigner (CNA): GitHub_M
CVSS severity: HIGH
CVSS score: 7.6 / 10
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N
Effective score: 7.6 / 10 HIGH source: CNA overview
CWE(s): CWE-79
Reserved: 2026-08-20
Published: 2026-09-23 18:53 UTC
Last updated: 2026-09-23 19:28 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/77xxx/CVE-2026-77394.json
Linked Threat: CVE-2026-77394 — OpenC3 COSMOS: Stored, cross-user XSS via Telemetry screen BUTTON widget

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2026-09-23 19:19:15 UTC
NVD last modified: 2026-09-23 20:17:15 UTC
NVD CVSS v3.1: 7.6 / 10 HIGH source: security-advisories@github.com
NVD CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N
Exploitability subscore: 2.3 / 10
Impact subscore: 4.7 / 10

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2026-85564
Assigner: GitHub_M
Published: Sep 23, 2026, 6:53:20 PM
Updated: Sep 23, 2026, 7:28:31 PM
EUVD base score (CVSS 3.1): 7.6 / 10
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N
EUVD-reported EPSS: 0.0000
Vendors: OpenC3
Products: cosmos (5.0.6, < 7.3.0)
Aliases: GHSA-gvf2-2rh5-mpgf

ENISA 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.

EUVD references (4)

Affected products (1)

Vendor	Product	Versions	Platforms
OpenC3	cosmos	`>= 5.0.6, < 7.3.0` (affected)	—

Vendor references (4)

References embedded in the original CVE record by the assigning CNA.

https://github.com/OpenC3/cosmos/security/advisories/GHSA-gvf2-2rh5-mpgf x_refsource_CONFIRM
https://github.com/OpenC3/cosmos/pull/3560 x_refsource_MISC
https://github.com/OpenC3/cosmos/commit/10371f8f410b9ad588f98dfa3befaaacb6587cd3 x_refsource_MISC
https://github.com/OpenC3/cosmos/releases/tag/v7.3.0 x_refsource_MISC

Web references (0)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

No web references attached yet.

NVD-tagged references (5)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

https://github.com/OpenC3/cosmos/commit/10371f8f410b9ad588f98dfa3befaaacb6587cd3 security-advisories@github.com
https://github.com/OpenC3/cosmos/pull/3560 security-advisories@github.com
https://github.com/OpenC3/cosmos/releases/tag/v7.3.0 security-advisories@github.com
https://github.com/OpenC3/cosmos/security/advisories/GHSA-gvf2-2rh5-mpgf security-advisories@github.com
https://github.com/OpenC3/cosmos/security/advisories/GHSA-gvf2-2rh5-mpgf 134c704f-9b21-4f2e-91b3-4a467353bcc0

Remediations (10)

Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.

CVE-2026-69414 ShieldBreak Zero-Day: No Patch, and CISA BOD 26-04 Gives ...

web:blog.qualys.com

What can I do before Microsoft releases a patch ? Qualys TruRisk™ Eliminate provides a recommended mitigation for CVE - 2026 -69414 that can be applied to affected systems while Microsoft works on a fix . Assets can then be reassessed in Qualys VMDR to verify the remediation outcome.

2026-09-24 11:12 UTC
CVE-2026-77394 - Exploits & Severity - Feedly

web:feedly.com

CVE-2026-77394 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (CWE-79)

2026-09-24 11:12 UTC
Security Update Guide - Microsoft

web:msrc.microsoft.com

The Microsoft Security Response Center (MSRC) investigates all reports of security vulnerabilities affecting Microsoft products and services, and provides the information here as part of the ongoing effort to help you manage security risks and help keep your systems protected.

2026-09-24 11:12 UTC
Security Update Guide - Microsoft Security Response Center

web:msrc.microsoft.com

Security Update Guide - Microsoft Security Response Center

2026-09-24 11:12 UTC
Microsoft Patch Tracker (September 2026): Exploit-Ranked | Senserva

web:senserva.com

Every Microsoft security patch (KB) and the CVEs it fixes, with severity, CVSS, and CISA KEV status. Cross-linked to the CVE reference.

2026-09-24 11:12 UTC
March 10, 2026—Hotpatch KB5079420 (OS Builds 26200.7979 and 26100.7979 ...

web:support.microsoft.com

This Hotpatch update for Windows 11, version 25H2 and 24H2 (KB5079420), improves functionality, performance, and reliability. To learn more about differences between security updates, optional non-security preview updates, out-of-band (OOB) updates, and continuous innovation, see Windows monthly updates explained. For information on Windows update terminology, see the different types of ...

2026-09-24 11:12 UTC
SAP Security Patch Day - June 2026

web:support.sap.com

SAP security Patch Day Bulletin This post shares the information on security notes that remediate vulnerabilities discovered in SAP products. SAP strongly recommends that the customer visits the support portal and applies patches on priority to protect their SAP landscape. On 9th of June 2026 , SAP security patch day saw the release of 15 new security notes.

2026-09-24 11:12 UTC
DSA-2026-359: Security Update for Dell OpenManage Enterprise ...

web:www.dell.com

Dell OpenManage Enterprise remediation is available for multiple security vulnerabilities that may be exploited by malicious users to compromise the affected system.

2026-09-24 11:12 UTC
Oracle Critical Patch Update Advisory - July 2026

web:www.oracle.com

This Critical Patch Update contains 1448 new security patches across the product families listed below. Please note that a My Oracle Support (MOS) note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at July 2026 Critical Patch Update: Executive Summary and Analysis.

2026-09-24 11:12 UTC
Patch Tuesday September 2026: Security Updates & CVE Analysis

web:zecurit.com

Get the complete breakdown of Microsoft's September 2026 Patch Tuesday. We analyze the latest security updates and all critical CVEs .

2026-09-24 11:12 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-77394.json.

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