CVE-2026-125361: Tencent BrowserSkill through 0.4.2 Missing Authentication in Local WebSocket Transport
Tencent BrowserSkill through 0.4.2 contains a missing authentication vulnerability that allows local attackers to impersonate the bsk daemon because remoteSocket() connects to the loopback WebSocket without credentials or peer verification. Attackers who bind the daemon port before it starts or after it exits receive the extension's full tool surface, including evaluate, to run JavaScript through CDP in logged-in browser tabs.
Affected Software
Event History
Frequently Asked Questions
Who is exposed to this issue?
Users of Tencent BrowserSkill through version 0.4.2 are exposed when the browser extension connects to a service on the local loopback WebSocket transport. The attacker must have local access sufficient to bind the daemon port before the daemon starts or after it exits.
What can a successful attacker do?
A local attacker can impersonate the bsk daemon and obtain the extension's full tool surface. This includes evaluate, which can run JavaScript through CDP in logged-in browser tabs.
Does exploitation require browser interaction or remote network access?
No user interaction is required. The issue is described as local-only because exploitation depends on binding the loopback daemon port; the provided data does not indicate remote network exposure.
What condition indicates a system may already be vulnerable?
A system may be vulnerable if it runs Tencent BrowserSkill version 0.4.2 or earlier and its extension uses remoteSocket() to connect to the local daemon WebSocket without credentials or peer verification. Exposure is particularly relevant during daemon startup and after daemon shutdown, when another local process could bind the port.