CVE-2026-39969: TypeBot Auth Bypass Vulnerability

CVE-2026-39969 Overview

CVE-2026-39969 affects TypeBot, an open-source chatbot builder, in versions 3.16.0 and prior. The WhatsApp Cloud API webhook endpoint fails to verify the x-hub-signature-256 HMAC signature that Meta includes in every webhook delivery. Attackers can send spoofed webhook payloads to the endpoint POST /v1/workspaces/{workspaceId}/whatsapp/{credentialsId}/webhook without authentication. The path parameters workspaceId and credentialsId appear in server access logs, Meta's webhook dashboard, and integration documentation, making them recoverable by external parties. The flaw is tracked under CWE-287 (Improper Authentication) and is fixed in version 3.17.0.

Critical Impact
Unauthenticated attackers can trigger bot flows, drain API quotas, and interact with downstream services using the workspace owner's credentials.

Affected Products

TypeBot versions 3.16.0 and prior
TypeBot self-hosted deployments using WhatsApp Cloud API integration
TypeBot workspaces with configured WhatsApp credentials

Discovery Timeline

2026-05-22 - CVE-2026-39969 published to NVD
2026-05-23 - Last updated in NVD database

Technical Details for CVE-2026-39969

Vulnerability Analysis

The vulnerability resides in TypeBot's WhatsApp Cloud API webhook handler. Meta signs every webhook delivery with an HMAC-SHA256 signature transmitted in the x-hub-signature-256 header. TypeBot accepts incoming webhook requests without validating this signature against the configured app secret.

The webhook URL embeds tenant identifiers as path parameters. Both workspaceId and credentialsId are logged by upstream proxies, displayed in Meta's webhook configuration dashboard, and frequently shared during integration setup. Once an attacker obtains these identifiers, they can craft arbitrary JSON payloads mimicking Meta webhook events.

The attack consumes the workspace owner's WhatsApp API quota and triggers any bot flows wired to inbound message events. Downstream integrations called by those flows execute under the workspace owner's credentials, expanding the blast radius beyond TypeBot itself.

Root Cause

The webhook handler omits HMAC signature verification entirely. A correct implementation would compute HMAC-SHA256 over the raw request body using the Meta app secret and compare the result to the x-hub-signature-256 header using a constant-time comparison. TypeBot relies on the secrecy of path parameters for authentication, which is not a valid security boundary.

Attack Vector

An unauthenticated remote attacker who knows or guesses a target workspaceId and credentialsId sends a forged HTTP POST request to the webhook endpoint with a synthetic WhatsApp message payload. The server processes the payload as if it originated from Meta. The attacker requires no credentials, no user interaction, and no prior access to the TypeBot instance. Refer to GitHub Security Advisory GHSA-8vqp-r5w7-v47f for the maintainer's technical writeup.

Detection Methods for CVE-2026-39969

Indicators of Compromise

POST requests to /v1/workspaces/{workspaceId}/whatsapp/{credentialsId}/webhook lacking a valid x-hub-signature-256 header.
Webhook traffic originating from IP addresses outside Meta's documented IP ranges for WhatsApp Cloud API callbacks.
Unexpected spikes in bot flow executions or outbound API calls tied to WhatsApp-triggered flows.

Detection Strategies

Inspect web server and reverse proxy access logs for webhook POST requests and correlate the presence of the x-hub-signature-256 header against Meta's published source ranges.
Compare inbound webhook volume against actual end-user WhatsApp message activity to surface forged traffic.
Audit bot flow execution telemetry for triggers that lack a corresponding legitimate conversation in the WhatsApp Business Manager.

Monitoring Recommendations

Forward TypeBot application and access logs to a centralized logging platform and alert on anomalous webhook source IPs.
Track API quota consumption for the WhatsApp Cloud API credentials configured in each workspace and alert on sudden increases.
Monitor outbound HTTP calls from bot flows for unexpected destinations or volumes following webhook events.

How to Mitigate CVE-2026-39969

Immediate Actions Required

Upgrade TypeBot to version 3.17.0 or later, which adds HMAC signature verification to the WhatsApp webhook endpoint.
Rotate the Meta app secret and WhatsApp Cloud API credentials for any workspace that ran a vulnerable version.
Review bot flow execution history and outbound integration logs for unauthorized invocations.

Patch Information

The maintainer released the fix in TypeBot v3.17.0. The patch validates the x-hub-signature-256 header against an HMAC-SHA256 of the request body using the configured Meta app secret. Full details are available in GitHub Security Advisory GHSA-8vqp-r5w7-v47f.

Workarounds

Restrict access to the webhook endpoint at the reverse proxy or WAF layer to Meta's published WhatsApp Cloud API source IP ranges.
Place the TypeBot webhook behind an authenticating gateway that validates the x-hub-signature-256 header before forwarding requests.
Temporarily disable WhatsApp integrations on affected workspaces until the upgrade to v3.17.0 is complete.

bash

# Example NGINX snippet to enforce signature header presence before proxying
location ~ ^/v1/workspaces/.+/whatsapp/.+/webhook$ {
    if ($http_x_hub_signature_256 = "") {
        return 401;
    }
    proxy_pass http://typebot_backend;
}