# CVE-2026-59804: Midscene Bridge Server - Session Hijack via Unauthenticated WebSocket

> Unauthenticated attackers can hijack sessions, inject commands, exfiltrate data, or crash the Midscene Bridge Server via cross-origin WebSocket connections.

- **Severity:** High 7.6 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 8 Jul 2026
- **Updated:** 8 Oct 2026
- **Also known as:** GHSA-8rcx-4rjr-4wpf

## What is CVE-2026-59804?

CVE-2026-59804 is a high-severity missing authorization vulnerability in web-infra-dev midscene, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Midscene Bridge Server through 1.10.3, fixed in commit 86f4118, contains a missing authentication and CORS misconfiguration vulnerability that allows unauthenticated remote attackers to hijack active bridge sessions by opening a cross-origin WebSocket connection to the local Socket.IO server, which performs no Origin header validation and requires no authentication token. Attackers can connect from any web page visited by the victim to seize the single-client slot, intercept and inject automation commands, exfiltrate command-payload data, or unconditionally terminate the server by supplying the MIDSCENE_BRIDGE_SIGNAL_KILL query parameter.

Weakness: CWE-306 (Missing Authentication for Critical Functionality), CWE-1385 (Missing Origin Validation in WebSockets)

## Which versions are affected by CVE-2026-59804?


## How do I fix CVE-2026-59804?

No fix has been published for CVE-2026-59804 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-59804 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59804 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59804 and fix it if it is affected.

What it is: CVE-2026-59804 is a high-severity missing authorization vulnerability in web-infra-dev midscene, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59804 exists.

Affected product: web-infra-dev midscene. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-59804/ (Markdown: https://insights.sbomify.com/CVE-2026-59804/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59804
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59804
- OSV: https://osv.dev/vulnerability/CVE-2026-59804

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59804/
Summaries are generated and may contain mistakes; the official description above is the record.