Compliance Impact

The provided information does not explicitly address how the vulnerability impacts compliance with common standards and regulations such as GDPR or HIPAA.

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Executive Summary

This vulnerability exists in Nanobot versions prior to 0.2.1 and involves a server-side request forgery (SSRF) issue in the Microsoft Teams channel handler.

Remote attackers can exploit this by sending a forged activity containing an attacker-controlled serviceUrl value to the Teams webhook.

This allows attackers to poison the stored conversation reference, causing the bot to send subsequent replies with Authorization header requests that include Bot Framework bearer tokens to an attacker-controlled host.

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Impact Analysis

The vulnerability can lead to unauthorized exfiltration of Bot Framework bearer tokens.

Attackers gaining these tokens could impersonate the bot or access sensitive communications, potentially leading to further attacks or data breaches.

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Detection Guidance

Detection of this vulnerability involves monitoring for suspicious inbound activities to the Microsoft Teams webhook that contain forged or attacker-controlled serviceUrl values. Since the vulnerability allows poisoning of stored conversation references, network or system logs should be inspected for outbound requests from the bot containing Authorization headers sent to unusual or untrusted hosts.

Commands or methods to detect this may include:

• Reviewing web server or application logs for outbound requests with Authorization headers targeting non-Microsoft or unexpected domains.
• Using network monitoring tools (e.g., tcpdump, Wireshark) to capture outbound HTTP requests from the bot process and filtering for Authorization headers.
• Checking the stored conversation references or bot configuration for serviceUrl values that do not match the trusted Microsoft Teams service hosts.
• If possible, enabling debug or verbose logging in the Nanobot application to log inbound activities and their serviceUrl fields.

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Mitigation Strategies

Immediate mitigation steps include updating Nanobot to version 0.2.1 or later, which contains the fix for this vulnerability by enforcing a trusted-host boundary for Microsoft Teams service URLs.

Additional mitigation measures are:

• Ensure that Teams webhook authentication is enabled and properly configured (validateInboundAuth=true) to block forged inbound activities via Bot Framework JWT validation.
• Verify that only HTTPS URLs matching the trusted Microsoft Teams service host patterns are accepted and stored as conversation references.
• Prune or remove any existing conversation references that contain untrusted or suspicious serviceUrl values.
• Review and apply the security patches or configuration changes described in the Nanobot repository pull request addressing CVE-2026-49139.

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