CVE-2026-77394
OpenC3 COSMOS: Stored, cross-user XSS via Telemetry screen BUTTON widget
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High7.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N |
| NVDNVD · Deferred | 3.1 | High7.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N |
- EPSS (exploitation in 30 days)
- 0.42% · top 64% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.6.
Weakness
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- npm@openc3/vue-commonGHSA-gvf2-2rh5-mpgf (opens in a new tab)
References (4)
- https://github.com/OpenC3/cosmos/security/advisories/GHSA-gvf2-2rh5-mpgf (opens in a new tab)x_refsource_CONFIRMexploit
- https://github.com/OpenC3/cosmos/pull/3560 (opens in a new tab)x_refsource_MISC
- https://github.com/OpenC3/cosmos/commit/10371f8f410b9ad588f98dfa3befaaacb6587cd3 (opens in a new tab)x_refsource_MISC
- https://github.com/OpenC3/cosmos/releases/tag/v7.3.0 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-gvf2-2rh5-mpgf (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-77394)Record last updated .