The flaw in OpenClaw’s Canvas Host Route allows a remote attacker to trigger a denial of service by sending a crafted request that forces the server to read and buffer an entire file via readFile() without imposing a size limit. This excessive memory allocation can exhaust server resources and cause the process to become unresponsive. The vulnerability exists in the createCanvasHostHandler function of extensions/canvas/src/host/server.ts and is exploitable over the network as the attacker does not require local access.

Affected software is OpenClaw up to version 2026.9.5, specifically the Canvas Host Route component. Users running any release prior to 2026.9.5 are susceptible; the weakness originates from the server.ts handler and is unrelated to other modules.

The CVSS score of 5.3 indicates a medium severity, but the flaw is publicly known and has a functioning exploit, so organizations should treat it as a risk that could be leveraged to disrupt services. The EPSS score is unavailable, yet the lack of a protective size limit and the remote attack vector increase the practical likelihood of exploitation. The flaw is not currently listed in the CISA KEV catalog, yet the existence of a published exploit and lack of vendor remediation suggest that the potential for widespread DoS attacks remains significant.