CVE-2026-49139: Nanobot < 0.2.1 SSRF via Microsoft Teams Channel serviceUrl Poisoning

Synopsis

Server-side request forgery (SSRF) in Nanobot, a Microsoft Teams bot framework library, affects all versions before 0.2.1. The vulnerability is reachable over the network with no authentication required: an attacker sends a crafted inbound activity to the Teams webhook with a forged serviceUrl, poisoning the stored conversation reference so the bot's subsequent replies carry Bot Framework bearer tokens to an attacker-controlled host. Successful exploitation results in theft of those bearer tokens, which can then be used to impersonate the bot and interact with downstream Microsoft services. A patched-image rebuild at version 0.2.1 is available on HarborGuard for environments running an affected version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must reach the Nanobot Teams webhook endpoint over the network to deliver the forged activity payload.

• AuthenticationNot required

  No credentials or session are needed; the Teams webhook accepts inbound activities without prior authentication by the sender.

• Victim interactionNot required

  No user action is required; the bot processes the malicious activity and forwards tokens autonomously.

• Attack complexityDetail

  Base exploit logic is straightforward, but the CVSS AT:P token indicates a prerequisite condition (the bot must have an active conversation reference that can be poisoned) must be in place before the attack succeeds.

Blast Radius

• Reads Bot Framework bearer tokens transmitted in Authorization headers, giving the attacker credentials to call Bot Framework and Microsoft Graph APIs as the bot identity.
• Modifies downstream bot behavior by redirecting reply traffic, allowing the attacker to intercept or alter messages the bot sends to users.
• Grants persistent access as long as the poisoned conversation reference remains stored, meaning token exfiltration can continue across multiple bot interactions without re-exploitation.