langbot-app LangBot up to 0.4.17 Plugin Runtime plugin_debug_key improper authentication

Summaryinfo

A vulnerability labeled as critical has been found in langbot-app LangBot up to 0.4.17. Affected by this vulnerability is an unknown functionality of the component Plugin Runtime. Executing a manipulation of the argument plugin_debug_key can lead to improper authentication. This vulnerability is handled as CVE-2026-90938. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability has been found in langbot-app LangBot up to 0.4.17 and classified as critical. This vulnerability affects an unknown part of the component Plugin Runtime. The manipulation of the argument plugin_debug_key with an unknown input leads to a improper authentication vulnerability. The CWE definition for the vulnerability is CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability was named CVE-2026-90938 since 09/14/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/14/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

• langbot-app

Name

• LangBot

Version

• 0.4.0
• 0.4.1
• 0.4.2
• 0.4.3
• 0.4.4
• 0.4.5
• 0.4.6
• 0.4.7
• 0.4.8
• 0.4.9
• 0.4.10
• 0.4.11
• 0.4.12
• 0.4.13
• 0.4.14
• 0.4.15
• 0.4.16
• 0.4.17

Website

• Product: https://github.com/langbot-app/LangBot/

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