Nanobot Server-Side Request Forgery Vulnerability in Microsoft Teams Channel Handler

A server-side request forgery (SSRF) vulnerability has been identified in Nanobot versions prior to 0.2.1. This vulnerability resides in the Microsoft Teams channel handler, where remote attackers can exfiltrate Bot Framework bearer tokens. Exploitation involves sending a forged activity with an attacker-controlled serviceUrl, which poisons the stored conversation reference. As a result, subsequent bot replies include token-bearing Authorization header requests sent to an attacker-controlled host.

Impact

Exploitation of this vulnerability allows for the unauthorized exfiltration of Bot Framework bearer tokens, which could be used to impersonate the bot or access its resources.

Reproduction

To reproduce this vulnerability, send a crafted inbound activity to the Microsoft Teams webhook with a fake serviceUrl controlled by the attacker. This will poison the conversation reference. Then, when the bot replies, it will include an Authorization header with the Bot Framework bearer token, sending it to the attacker's host.

Remediation

Users can update to Nanobot version 0.2.1 or later, where this vulnerability has been fixed.