CVE-2026-42086 | OpenC3 COSMOS: Self-XSS in the Command Sender

Exp

OpenC3 COSMOS provides the functionality needed to send commands to and receive data from one or more embedded systems. Prior to version 7.0.0, the Command Sender UI uses an unsafe eval() function on array-like command parameters, which allows a user-supplied payload to execute in the browser when sending a command. This creates a self-XSS risk because an attacker can trigger their own script execution in the victim’s session, if allowed to influence the array parameter input, for example via phishing. If successful, an attacker may read or modify data in the authenticated browser context, including session tokens in local storage. This issue has been patched in version 7.0.0.

Published: 2026-05-04 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-42086 is rated Exploit Available (50/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.20%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-42086

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-42086

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.03% 0.20% +0.17%
2 2026-05-05 — 0.03% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-42086

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.6 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.1 2.5 [email protected]

Weakness enumeration for CVE-2026-42086

GitHub Security Advisory for CVE-2026-42086

GHSA-ffq5-qpvf-xq7x · Severity: medium · Ecosystem: rubygems — OpenC3 COSMOS is Vulnerable to Self-XSS Through the Command Sender

Affected software / configurations for CVE-2026-42086

Vendor Product Version Raw CPE
openc3 cosmos < 7.0.0 cpe:2.3:a:openc3:cosmos:*:*:*:*:open_source:*:*:*
openc3 cosmos 7.0.0 cpe:2.3:a:openc3:cosmos:7.0.0:rc1:*:*:open_source:*:*:*
openc3 cosmos 7.0.0 cpe:2.3:a:openc3:cosmos:7.0.0:rc2:*:*:open_source:*:*:*
openc3 cosmos 7.0.0 cpe:2.3:a:openc3:cosmos:7.0.0:rc3:*:*:open_source:*:*:*

References for CVE-2026-42086

cvelogic Threat Intelligence