CVE-2026-123139 Code injection in Neon
A malicious browser extension can take control of the browser via MCP Hub commands to Opera Neon's Browser Operator extension.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Harmful if only installed
- No
- Needs a specific call
- No
- Fix
- None listed
What is CVE-2026-123139?
CVE-2026-123139 is a medium-severity code injection vulnerability in Opera Neon, published on 12 Nov 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
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.
Weakness: CWE-940
Which versions are affected by CVE-2026-123139?
An affected version is exposed as installed. No special setting or call is needed.
How do I fix CVE-2026-123139?
No fix has been published for CVE-2026-123139 yet. Limit exposure of the affected software until one is available.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-123139 being exploited?
There is no known exploitation of CVE-2026-123139 in the wild and no public exploit code.
Sources
Also known as GHSA-2f45-6797-cj93.