CVE-2026-90938 langbot-app CVE debrief

Who should care

Defenders responsible for systems using LangBot plugin runtime should assess exposure and prioritize remediation due to the high severity of this vulnerability. They should verify if the plugin_debug_key is set and not empty, restrict access to port 5401, and implement authentication for the WebSocket server. Additionally, defenders should review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance. They

Why it matters

CVE-2026-90938 is a high-severity vulnerability in LangBot's plugin runtime that allows unauthenticated plugin registration and sensitive information exposure. Defenders should assess exposure, prioritize remediation, and verify plugin_debug_key configuration.

• Remote attackers can access sensitive information, including private chats and user IDs
• Arbitrary message injection and execution of forged replies are possible
• Enumeration of bot UUIDs and invocation of configured LLM models can occur
• Registration of malicious tools that feed every user's LLM pipeline is a concern

Technical summary

The LangBot plugin runtime (pip package langbot_plugin) through 0.4.17 starts a debug WebSocket server on 0.0.0.0:5401 without proper authentication, allowing remote attackers to register arbitrary 'debug plugins' and access sensitive information, including private chats and user IDs. The plugin_debug_key, which gates authentication, defaults to an empty string and is not set by the upstream repository, Docker image, or docker-compose. This oversight enables attackers to inject forged replies, send messages as any configured bot, enumerate bot UUIDs, invoke configured LLM models, and register malicious tools that feed every user's LLM pipeline.

Defensive priority

High priority for defenders to assess exposure and remediate

Recommended defensive actions

• Assess exposure by checking if LangBot plugin runtime version 0.4.17 or earlier is in use
• Verify if the plugin_debug_key is set and not empty
• Restrict access to port 5401
• Implement authentication for the WebSocket server
• Update to a patched version if available

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its high severity and potential impacts. However, the corpus does not establish versions beyond 0.4.17, exploitation details, or remediation for all affected systems. Defenders should verify plugin_debug_key configuration and assess exposure by checking if LangBot plugin runtime version 0.4.17 or earlier is in use. The CVE Program record (CVE-2026-90938) and NVD detail page offer source-provided CVE metadata and vulnerability assessments. Additional source

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.