GHSA-MF5G-6R6F-GHHM: Pre-Authentication Rate-Limit Bypass in OpenClaw Synology Chat Plugin

The OpenClaw application utilizes the synology-chat plugin to integrate with Synology's messaging ecosystem. This plugin exposes a webhook endpoint designed to receive inbound HTTP POST requests containing chat payloads. Authentication for this endpoint relies entirely on a pre-shared secret token verified during payload processing.

An Improper Restriction of Excessive Authentication Attempts (CWE-307) vulnerability exists within the webhook validation implementation. The system fails to enforce source-based throttling on failed authentication attempts. Consequently, an attacker can submit continuous HTTP POST requests to guess the authentication token without encountering any lockout or rate-limiting restrictions.

Successful exploitation grants an attacker the ability to spoof messages as any user within the Synology Chat integration. This unauthorized access enables direct interaction with the OpenClaw AI assistant, presenting risks of sensitive data disclosure, manipulation of the AI's context, and the potential triggering of downstream automated actions configured within the AI's toolset.

The underlying flaw resides in the structural ordering of operations within the authorizeSynologyWebhook function. When a request arrives, the webhook handler first parses the incoming JSON or form-encoded payload to extract the token and user_id fields. The application immediately compares the user-provided token against the server's configured secret token.

The application does implement a rate-limiting mechanism via the rateLimiter.check() function. However, this defensive check executes strictly after the token validation step succeeds. Furthermore, the rate limiter utilizes the untrusted user_id field provided in the payload as its tracking key, rather than utilizing the network-layer source IP address.

Because failed token validations result in an immediate HTTP 401 Unauthorized response prior to reaching the rate-limiting code block, the system records no state regarding the failed authentication attempt. The application inadvertently drops the failure tracking context, allowing unauthenticated attackers to iterate through token permutations indefinitely without triggering an HTTP 429 Too Many Requests response.

The vulnerability stems from the sequence of operations in the authentication flow. In the vulnerable implementation, the code performs the cryptographic equality check on the token and issues an early return if the validation fails. The state-tracking mechanism required to detect brute-force behavior is entirely bypassed during an attack.

// Vulnerable Implementation Pattern
const payload = req.body;
 
// Token checked FIRST. Fails return immediately.
if (!validateToken(payload.token, account.token)) {
    return res.status(401).send('Unauthorized');
}
 
// Rate limit checked SECOND, using untrusted payload data.
if (!rateLimiter.check(payload.user_id)) {
    return res.status(429).send('Too Many Requests');
}

The official patch (commit 0b4d07337467f4d40a0cc1ced83d45ceaec0863c) resolves this by introducing an InvalidTokenRateLimiter class. This component shifts the tracking metric from the payload's user_id to the incoming network request's source IP address. It also ensures that the state is recorded regardless of the validation outcome.

// Patched Implementation Pattern
const clientIp = req.ip;
 
// 1. Enforce rate limit using source IP before any processing
if (invalidTokenRateLimiter.isRateLimited(clientIp)) {
    return res.status(429).send('Too Many Requests');
}
 
const payload = req.body;
 
// 2. Validate token, recording failures to the state tracker
if (!validateToken(payload.token, account.token)) {
    invalidTokenRateLimiter.recordFailure(clientIp);
    return res.status(401).send('Unauthorized');
}

Exploiting this vulnerability requires network visibility to the OpenClaw instance's public webhook endpoint. The attacker needs no prior authentication, specific system privileges, or specialized configurations beyond the presence of an active synology-chat plugin. The attack surface is exposed to any host capable of routing HTTP traffic to the target URL.

The attacker constructs a high-volume stream of HTTP POST requests directed at the webhook path. Each request contains a structurally valid Synology Chat JSON or URL-encoded payload. The attacker programmatically increments or mutates the token field within the payload across subsequent requests, functioning as a standard dictionary or brute-force attack.

The server responds with HTTP 401 (Unauthorized) for incorrect guesses. The attacker monitors the HTTP response codes, continuing the attack loop until an HTTP 204 (No Content) or 200 (OK) response is observed. This state change definitively indicates that the current token permutation successfully authenticated the payload. The official test suite explicitly demonstrates this methodology by programmatically looping requests to verify the absence of an HTTP 429 response.

Successfully brute-forcing the webhook token compromises the primary authentication boundary for the Synology Chat integration. The immediate impact allows an attacker to inject arbitrary messages into the OpenClaw system, perfectly masquerading as legitimate, trusted users. The server processes these injected payloads precisely as it would authentic traffic originating from the Synology infrastructure.

Secondary consequences arise from the capabilities granted to the OpenClaw AI assistant. By spoofing messages, the attacker interfaces directly with the AI engine. Depending on the configured permissions and loaded tools, the adversary can extract sensitive data from the AI's context memory, execute automated backend operations, or manipulate the AI's internal state to facilitate social engineering attacks against genuine users.

Security researchers analyzing the post-patch environment should note the specific constraints of the fixed implementation. The InvalidTokenRateLimiter enforces a threshold of 10 requests per minute and tracks up to 5,000 unique IP addresses via a Least Recently Used (LRU) cache. Attackers controlling a distributed proxy network exceeding 5,000 IP addresses can intentionally flood the limiter to evict their primary attack nodes, resetting the failure counts and sustaining low-volume distributed brute-force operations.

The primary remediation strategy requires administrators to upgrade the openclaw npm package to version 2026.3.26 or later. This release incorporates the 0b4d07337467f4d40a0cc1ced83d45ceaec0863c commit, which correctly positions the IP-based rate limiting logic prior to the token evaluation phase. Applying this update immediately halts unauthenticated, single-source token brute-forcing.

The implementation of the IP-based rate limiter introduces strict environmental dependencies regarding request origin visibility. Deployments situating OpenClaw behind reverse proxies, load balancers, or Web Application Firewalls must verify the correct configuration of X-Forwarded-For or equivalent headers. Failure to reliably pass the true client IP address causes the rate limiter to track the proxy's IP, invariably resulting in widespread denial of service for legitimate traffic once the 10-request threshold is breached.

Independent of application-level patches, administrators must implement strong cryptographic controls for the webhook tokens themselves. Organizations must rotate all existing Synology Chat webhook tokens, replacing them with high-entropy strings of at least 32 alphanumeric characters. High-entropy tokens render brute-force attacks mathematically unfeasible, neutralizing the vulnerability entirely regardless of application layer throttling deficiencies.