CVE-2026-100571 in OpenClaw
Summary
by MITRE • 09/26/2026
OpenClaw (npm package 'openclaw') versions >= 2026.6.6 and < 2026.8.1 apply the SMS webhook invalid-request rate limit before Twilio signature verification and identify clients only by the raw proxy socket address. In deployments where the SMS/Twilio webhook sits behind a trusted reverse proxy or tunnel so that multiple external clients share one socket address, an unauthenticated remote sender can exhaust the shared pre-authentication rate-limit budget with invalid requests, causing subsequent correctly signed Twilio callbacks to receive HTTP 429 responses. The result is temporary inbound SMS loss while the shared window remains exhausted; the attacker cannot forge a callback or access message data. Fixed in 2026.8.1.
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Analysis
by VulDB Data Team • 09/26/2026
The vulnerability identified in OpenClaw versions greater than or equal to 2026.6.6 and less than 2026.8.1 represents a critical flaw in the authentication and rate-limiting logic for SMS webhook endpoints, specifically those integrated with Twilio services. The core technical deficiency lies in the sequence of operations performed by the application upon receiving an incoming HTTP request. Instead of first verifying the cryptographic signature provided by Twilio to authenticate the source of the message, OpenClaw applies a strict invalid-request rate limit based on the client's IP address or proxy socket identifier before any authentication checks occur. This ordering error creates a window where unauthenticated traffic is processed and counted against a shared resource pool without establishing trustworthiness first.
In typical enterprise deployments, SMS webhooks are often situated behind trusted reverse proxies, load balancers, or tunneling services to manage SSL termination, routing, and security policies. In such architectures, multiple external clients may share a single public-facing socket address as seen by the backend application server. Because OpenClaw identifies clients solely by this raw proxy socket address rather than inspecting headers that might distinguish individual tenants or using post-authentication identifiers, all traffic arriving through that shared IP is treated as originating from a single entity. This architectural assumption becomes a severe liability when combined with the premature rate-limiting logic, allowing any remote actor to impact services for legitimate users sharing the same network path.
An unauthenticated remote attacker can exploit this flaw by sending a high volume of malformed or invalid SMS webhook requests to the affected endpoint. Since these requests are processed before signature verification, they consume the pre-authentication rate-limit budget allocated to that shared socket address. Once this budget is exhausted, the application begins rejecting subsequent legitimate HTTP 429 responses for all traffic associated with that IP range. Consequently, correctly signed and authenticated Twilio callbacks from actual users or systems are blocked by the server's own security controls. This results in a temporary but complete loss of inbound SMS functionality for any service relying on those shared credentials or endpoints until the rate-limiting window expires or is manually reset.
The operational impact of this vulnerability is primarily availability-focused, classified under Denial of Service against specific communication channels rather than data exfiltration or system compromise. The attacker cannot forge valid Twilio callbacks due to the lack of signing keys, nor can they access sensitive message data because authentication failures prevent further processing beyond the rate limit check. However, the disruption to inbound SMS services can have significant downstream effects on applications that rely on these messages for two-factor authentication, critical alerts, or user verification processes. The temporary nature of the outage means recovery is automatic upon window expiration, but during that period, business continuity and security workflows dependent on real-time SMS delivery are severely degraded.
From a standards perspective, this vulnerability aligns with CWE-780: Use of RSA Algorithm for Key Management if we consider the improper handling of cryptographic verification timing, though more accurately it maps to CWE-400: Uncontrolled Resource Consumption due to the exhaustion of rate-limiting resources by unauthenticated actors. In terms of the MITRE ATT&CK framework, this behavior facilitates a Denial of Service (T1499) attack vector where an adversary disrupts service availability through resource exhaustion. It also reflects CWE-284: Improper Access Control because the system fails to properly restrict access based on authentication status before applying restrictive controls that affect legitimate users.
Mitigation strategies must address both the immediate software defect and broader architectural assumptions regarding client identification. The primary remediation is to upgrade OpenClaw to version 2026.8.1 or later, where this ordering issue has been resolved by ensuring signature verification occurs prior to rate-limiting checks. For organizations unable to patch immediately due to operational constraints, temporary workarounds include configuring the reverse proxy to assign unique IP addresses or use distinct routing rules for different tenants if possible, thereby isolating their traffic from shared socket-based limits. Additionally, implementing WAF (Web Application Firewall) rules that drop malformed requests before they reach the application server can reduce the load on OpenClaw's internal rate limiter. Long-term architectural reviews should ensure that authentication and authorization checks are always performed early in the request lifecycle to prevent unauthenticated actors from consuming shared resources or triggering side effects intended for authenticated sessions.