Vulnerability record · CVE-2026-123139 · published 12 November 2026

CVE-2026-123139: Improper verification of the source of a communication channel vulnerability in Opera Neon on macOS and Window…

Improper verification of the source of a communication channel vulnerability in Opera Neon on macOS and Windows allows a malicious browser extension to take control of the browser by sending commands through MCP Hub to the built-in Browser Operator extension. This issue affects Opera Neon MCP Hub extension: 0.0.1.

5.8 CVSS 4.0 Medium CWE-940 · CWE-940 Received

5.8CVSS 4.0 base score

-EPSS exploitation probability, 30 days

NoNot in CISA KEV

0Affected product versions listed by NVD

1References

12 Nov 2026Last modified by NVD

Description

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:L/SI:L/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

Link	Tags
https://security.opera.com/en/improper-verification-of-source-of-a-communication-channel-opera-security-advisories/

Track CVE-2026-123139 inside VULONE

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-123139), CISA KEV, FIRST EPSS. This page is refreshed as NVD updates the record.