CVE-2026-35623: 
OpenClaw (formerly Moltbot or Clawdbot) vulnerability analysis and mitigation

CVE-2026-35623 is a missing rate limiting vulnerability in the BlueBubbles webhook authentication component of OpenClaw, an npm package. The flaw allows unauthenticated remote attackers to brute-force weak webhook passwords without any throttling or account lockout mechanism. All versions of OpenClaw up to and including 2026.3.24 (for Node.js) are affected; version 2026.3.25 contains the fix. The vulnerability carries a CVSS v3.1 base score of 6.5 (Medium) and a CVSS v4.0 base score of 6.3 (Medium) (GitHub Advisory, GHSA-rc8f-r29c-chr6). The advisory was originally published on April 9–10, 2026, with the patch committed on April 16, 2026 (GitHub Commit).

The root cause is classified as CWE-307 (Improper Restriction of Excessive Authentication Attempts) and secondarily CWE-521 (Weak Password Requirements). Prior to the fix, the BlueBubbles webhook handler in OpenClaw rejected incorrect passwords immediately without any throttling, allowing an attacker to submit an unlimited number of password guesses to the webhook endpoint (via the password query parameter or x-guid header) in rapid succession. The fix, introduced in commit 5e08ce36d522a1c96df2bfe88e39303ae2643d92, implements a fixed-window rate limiter (createFixedWindowRateLimiter) keyed by normalized webhook path and resolved client IP address, with a default budget of 120 requests per minute; it also adds proper trusted-proxy and X-Real-IP header handling to prevent rate-limit bypass via IP spoofing (GitHub Advisory, GitHub Commit).

Successful exploitation allows an unauthenticated remote attacker to compromise webhook authentication credentials through brute force, gaining unauthorized access to the webhook endpoint. This results in limited confidentiality impact (unauthorized information disclosure from webhook data) and limited integrity impact (unauthorized modification or injection of webhook-delivered data), with no direct availability impact. The scope is limited to the vulnerable OpenClaw instance and its connected BlueBubbles integration; however, depending on what actions the webhook triggers, a compromised endpoint could facilitate further unauthorized operations within the integrated environment (GitHub Advisory, GHSA-rc8f-r29c-chr6).

There is no public proof-of-concept exploit code and no evidence of in-the-wild exploitation at this time (GHSA-rc8f-r29c-chr6). The EPSS score is approximately 0.047%, indicating a low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported. The attack is network-accessible and requires no privileges or user interaction, but exploitation is practically constrained by the need for the target to use a weak webhook password.

1. Reconnaissance: Identify internet-exposed OpenClaw instances running versions ≤ 2026.3.24 (npm package). Scan for the BlueBubbles webhook endpoint path (e.g., /bluebubbles/webhook or similar configured path).
2. Confirm endpoint: Send a test POST request to the webhook endpoint with an arbitrary password parameter (e.g., ?password=test or x-guid: test header) and observe a 401 Unauthorized response, confirming the endpoint is active and password-protected.
3. Brute-force password: Using a scripted HTTP client or tool (e.g., curl in a loop, hydra, or a custom script), submit rapid sequential POST requests to the webhook endpoint with incrementing or dictionary-based password candidates — e.g., POST /webhook?password=00000001, POST /webhook?password=00000002, etc. — exploiting the absence of rate limiting to iterate through candidates without throttling.
4. Detect successful authentication: Monitor HTTP responses; a non-401 response (e.g., 200 OK) indicates the correct password has been found.
5. Exploit access: Use the discovered webhook password to send crafted webhook payloads to the endpoint, potentially injecting malicious messages or triggering unauthorized actions within the BlueBubbles/OpenClaw integration (GitHub Advisory, GitHub Commit).

• Network: High volume of POST requests to the BlueBubbles webhook endpoint from a single IP address or small IP range in a short time window; requests containing sequential or dictionary-pattern values in the password query parameter or x-guid header.
• Logs: Repeated HTTP 401 responses in the web server or application access logs for the webhook endpoint path from the same source IP; sudden transition from 401 to 200 responses indicating a successful brute-force guess.
• Application: Unexpected or unauthorized webhook payloads being processed by the OpenClaw/BlueBubbles integration after a series of failed authentication attempts; webhook activity originating from unknown or untrusted IP addresses.

The primary remediation is to upgrade OpenClaw to version 2026.3.25 or later, which introduces fixed-window rate limiting on webhook authentication attempts (default: 120 requests/minute per client IP) and proper trusted-proxy IP resolution to prevent bypass (GitHub Advisory, GitHub Commit). As interim mitigations prior to upgrading: configure a strong, randomly generated webhook password to significantly reduce brute-force feasibility; place the webhook endpoint behind a reverse proxy or firewall that enforces its own rate limiting; and restrict webhook endpoint access to known trusted IP ranges. Monitor webhook endpoint logs for anomalous authentication failure patterns.

The vulnerability was reported by security researcher zpbrent and disclosed via the OpenClaw GitHub security advisory (GHSA-xq8g-hgh6-87hv), published March 26, 2026, ahead of the 2026.3.25 npm release (GitHub Advisory). VulnCheck independently published an advisory for the issue (GHSA-rc8f-r29c-chr6). No significant broader media coverage or notable social media discussion has been identified for this vulnerability.