CVE-2025-0741: Thesamur Embedai Auth Bypass Vulnerability

CVE-2025-0741 Overview

CVE-2025-0741 is an Improper Access Control vulnerability [CWE-284] affecting EmbedAI version 2.1 and below from Thesamur. The flaw resides in the /embedai/chats/send_message POST endpoint. An authenticated attacker can manipulate the chat_id parameter to inject messages into chat sessions belonging to other users. The vulnerability requires only low privileges and no user interaction, and it can be exploited over the network. The issue affects the integrity of user conversations without directly impacting confidentiality or availability.

Critical Impact
Authenticated attackers can write arbitrary messages into other users' chat sessions by tampering with the chat_id request parameter, undermining conversation integrity in EmbedAI deployments.

Affected Products

Thesamur EmbedAI version 2.1
Thesamur EmbedAI versions prior to 2.1
Deployments exposing the /embedai/chats/send_message endpoint

Discovery Timeline

2025-01-30 - CVE-2025-0741 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in the NVD database

Technical Details for CVE-2025-0741

Vulnerability Analysis

EmbedAI exposes a chat messaging endpoint at /embedai/chats/send_message that accepts a chat_id parameter in the POST body. The application fails to validate whether the authenticated user owns or has authorization to post into the referenced chat session. An attacker with valid credentials can substitute any chat_id value and inject arbitrary content into another user's conversation.

This behavior classifies the flaw as Improper Access Control [CWE-284], a form of Insecure Direct Object Reference. The impact is limited to integrity of stored chat data, matching the low-integrity, no-confidentiality, no-availability profile associated with the CVSS vector.

Because EmbedAI is often deployed as an embedded conversational agent for websites and applications, poisoned chat histories can be leveraged for social engineering, prompt injection against downstream language model interactions, or reputational abuse of the hosting platform.

Root Cause

The root cause is missing server-side authorization on the chat_id request parameter. The endpoint trusts the client-supplied identifier without verifying that the authenticated session owns the target chat resource. There is no ownership check binding the current user's session to the chat record referenced by chat_id.

Attack Vector

Exploitation requires the attacker to hold a valid EmbedAI account. The attacker authenticates, observes or enumerates valid chat_id values belonging to other users, and issues a crafted POST request to /embedai/chats/send_message with the target chat_id and attacker-controlled message content. No user interaction is required from the victim. The message appears in the victim's chat as if legitimately generated.

A verified proof-of-concept is not currently published, and no exploit is listed on CISA KEV. See the INCIBE Multiple Vulnerabilities Notice for advisory details.

Detection Methods for CVE-2025-0741

Indicators of Compromise

Unexpected messages appearing in end-user chat histories that do not correlate with the authenticated user's activity.
POST requests to /embedai/chats/send_message where the session user identifier does not match the owner of the referenced chat_id.
Sudden spikes in send_message calls originating from a single authenticated account across many distinct chat_id values.

Detection Strategies

Enable verbose HTTP request logging on the EmbedAI application server and correlate user_id with chat_id ownership.
Deploy a Web Application Firewall (WAF) rule to flag requests where the chat_id parameter does not resolve to a chat owned by the authenticated session.
Perform periodic database audits joining chat records with their message authors to identify mismatched writes.

Monitoring Recommendations

Alert on authenticated users iterating through sequential or randomized chat_id values within short time windows.
Monitor for anomalous message content patterns injected into multiple unrelated chats from a single source account.
Retain application and reverse-proxy logs long enough to reconstruct message provenance during incident response.

How to Mitigate CVE-2025-0741

Immediate Actions Required

Upgrade EmbedAI to a version released after 2.1 that addresses the Improper Access Control flaw once available from Thesamur.
Restrict access to the EmbedAI application to trusted users while a patch is applied, reducing the pool of accounts able to exploit the endpoint.
Audit chat message tables to identify and remediate any messages written under mismatched ownership.

Patch Information

Thesamur has been notified through the INCIBE-CERT advisory process. Consult the INCIBE Multiple Vulnerabilities Notice for the current patch status and refer to the official EmbedAI project channels for release notes covering versions after 2.1.

Workarounds

Add a reverse-proxy or API gateway rule that validates the chat_id parameter against the authenticated user's session before forwarding requests to /embedai/chats/send_message.
Disable or gate the send_message endpoint behind additional authorization middleware until an official fix is deployed.
Rotate credentials and invalidate active sessions for any account observed abusing the endpoint.

bash

# Example NGINX snippet to block unauthenticated or malformed send_message requests
location /embedai/chats/send_message {
    if ($request_method != POST) { return 405; }
    if ($http_authorization = "") { return 401; }
    proxy_pass http://embedai_backend;
}