CVE-2026-77394

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

Published: Sep 23, 2026Updated: Sep 23, 2026 Sources: CVE List NVDCWE-79

7.6HIGH

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.

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:LAttack Complexity

Low

PR:LPrivileges Required

Low

UI:RUser Interaction

Required

Scope

S:CScope

Changed

Impact

C:HConfidentiality

High

I:LIntegrity

Low

A:NAvailability

None

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Weaknesses

CWE-79

Affected Products

OpenC3

oss-project

cosmosOn-prem

OSS Libraries

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques

Execution

Initial Access

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References

https://github.com/OpenC3/cosmos/security/advisories/GHSA-gvf2-2rh5-mpgf

github.com

https://github.com/OpenC3/cosmos/pull/3560

github.com

https://github.com/OpenC3/cosmos/commit/10371f8f410b9ad588f98dfa3befaaacb6587cd3

github.com

and 1 more references View all →

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