# CVE-2026-123139: Opera Neon MCP Hub improper communication channel verification

Source: https://junglewise.ai/threats/cve-2026-123139-improper-verification-of-the-source-of-a-communication-channel  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-12. Updated: 2026-11-12  
License: CC BY 4.0 with a link back

CVE-2026-123139 · Severity: info · Published 2026-11-12

Opera Neon is a web browser for macOS and Windows that includes an MCP Hub extension for managing browser operations. A malicious browser extension can exploit improper verification in the MCP Hub to send unauthorized commands to the built-in Browser Operator extension, potentially taking full control of the browser and the user's browsing session.

Vendors: [Opera](https://junglewise.ai/threats/vendors/opera).

## Quick answers

**Is CVE-2026-123139 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-123139 being exploited in the wild.

**How severe is CVE-2026-123139?** Informational severity, published 12 November 2026.

**Which products and versions are affected?** Opera Neon 0.0.1.

**Is there a fix for CVE-2026-123139?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-123139 attacked?** It is attacked with local access, in a web application.

**Am I affected by CVE-2026-123139?** Check whether you run Opera Neon at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The MCP Hub extension in Opera Neon fails to properly verify the source of communication channel messages before relaying them to the Browser Operator extension, allowing any installed browser extension to send arbitrary commands. An attacker with ability to install a malicious extension can exploit this to achieve browser control without special privileges or user interaction beyond extension installation. A fix exists in versions beyond 0.0.1.

## Affected products

- Opera Neon 0.0.1

## Timeline

- 2026-11-12: disclosed

## References

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