CVE-2026-123139 PUBLISHED

Assigner: Opera
Reserved: 05.11.2026 Published: 12.11.2026 Updated: 12.11.2026

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.

Metrics

CVSS 4.0

CVSS Vector: 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
CVSS Score: 5.8

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Local	Confidentiality	High	Confidentiality	Low
Attack Complexity	Low	Integrity	High	Integrity	Low
Attack Requirements	None	Availability	None	Availability	None
Privileges Required	None
User Interaction	Passive

CVSS 4.0

Product Status

Vendor	Opera
Product	Neon
Versions	Default: unaffected Version 1.0.0 is affected

Credits

maitai finder

References

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

Problem Types

CWE-940 Improper verification of source of a communication channel CWE

Impacts

CAPEC-36 Using Unpublished Interfaces or Functionality