CVE-2026-63655

An unbounded MCP request can exhaust a tsParticles server

tsParticles · @tsparticles/mcp-server HTTP mode

First documented disclosure · Review checkpoint

Summary

An unauthenticated client can stream data into memory until the MCP service becomes unavailable.

Severity and exploitation evidence

High · 7.5/10 · CVSS 3.1. Severity source.

Exploitation not established: The advisory documents a proof of concept for the HTTP transport. It does not report a production victim.

Exploitation evidence source

Technical severity is not a measure of observed attacks or of risk to your deployment. Attempts, demonstrations, and successful compromise retain the qualifications in the source.

How the weakness works

The HTTP handler buffered each body chunk, concatenated the entire body and only then attempted to parse it. There was no cumulative size limit.

Conditions required

Network access to a server running the HTTP transport. The researcher identifies the official container’s default HTTP listener. The stdio transport is separate.

Potential impact

One request can consume process or container memory and disrupt all users of that process.

Affected versions and configurations

@tsparticles/mcp-server versions before 4.3.1, according to the CNA.

Fix and mitigation status

4.3.1 adds a cumulative 1 MiB body limit.

Practical next steps

Update to a supported release containing the limit. Bound ingress request sizes and isolate the service’s memory budget.

Operating lesson

Enforce byte limits as data arrives, before buffering it for JSON parsing.

Evidence and limits

The July 1 source change and release predate the July 2 advisory and November 4 CVE. The size-limit flaw and the separate malformed-JSON crash have distinct IDs.

Sources