LangBot Missing Signature Verification Allows Event Injection

Executive Summary

LangBot through version 4.11.0 has a vulnerability where it fails to verify the authenticity of incoming events. This allows unauthenticated attackers to forge Lark/Feishu events by bypassing signature checks. Attackers only need to know a bot's UUID to send fake im.message.receive_v1 or card.action.trigger events, which can manipulate the LLM pipeline, tools, and approvals as if they were another user.

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Detection Guidance

Detecting this vulnerability requires checking if LangBot instances are properly verifying event signatures. Monitor network traffic for POST requests to LangBot endpoints containing im.message.receive_v1 or card.action.trigger events. Verify if requests lack valid signatures despite having a bot UUID.

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Impact Analysis

This vulnerability could allow attackers to impersonate users in automated workflows, approve unauthorized actions, or inject malicious inputs into systems relying on LangBot. It may lead to unauthorized data access, fraudulent transactions, or disruption of automated processes.

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Compliance Impact

This vulnerability could violate compliance requirements by enabling unauthorized access or modifications to sensitive data processed by LangBot. GDPR may be impacted due to potential unauthorized data exposure, while HIPAA could be affected if protected health information is compromised through forged events.

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Mitigation Strategies

Update LangBot to the latest version (4.11.0 or higher) to ensure signature verification is enforced. Block unauthenticated POST requests to LangBot endpoints at the firewall level. Review logs for suspicious events and restrict bot UUID exposure.

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