---
id: CVE-2026-76893
title: >-
  tsParticles: A single anonymous MCP session can monopolize HTTP mode and deny
  new clients
summary: >-
  tsParticles is a TypeScript library for creating highly customizable particle
  animations. Prior to 4.3.2, the HTTP mode of @tsparticles/mcp-server reuses
  one stateful StreamableHTTPServerTransport for every client. An
  unauthenticated cli…
severity: medium
cvss: 6.9
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N'
cvssSource: cna
cwe:
  - CWE-400
vendor: tsparticles
product: tsparticles
affected:
  - tsparticles < 4.3.2
  - mcp-server < 4.3.2
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-11-05T20:20:28.208419Z'
exploitAvailable: true
published: '2026-11-04'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T20:20:55.808Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-76893'
references:
  - url: >-
      https://github.com/tsparticles/tsparticles/security/advisories/GHSA-h7c4-q426-7jh9
    label: >-
      https://github.com/tsparticles/tsparticles/security/advisories/GHSA-h7c4-q426-7jh9
  - url: 'https://github.com/tsparticles/tsparticles/pull/5888'
    label: 'https://github.com/tsparticles/tsparticles/pull/5888'
  - url: >-
      https://github.com/tsparticles/tsparticles/commit/d3b5672bd61bb847abfa21193c34eabf7aba6896
    label: >-
      https://github.com/tsparticles/tsparticles/commit/d3b5672bd61bb847abfa21193c34eabf7aba6896
tags:
  - cve.org
  - exploit-available
epss: 0.00291
epssPercentile: 0.21845
ingestedAt: '2026-11-05T22:38:31.768Z'
---

## Overview

tsParticles is a TypeScript library for creating highly customizable particle animations. Prior to 4.3.2, the HTTP mode of @tsparticles/mcp-server reuses one stateful StreamableHTTPServerTransport for every client. An unauthenticated client that sends the first initialize request without an mcp-session-id claims the shared transport state, causing later independent clients to receive Server already initialized and preventing them from establishing sessions until the process restarts. The first client's session remains functional. This issue is fixed in version 4.3.2.

## Affected

- `tsparticles < 4.3.2`
- `mcp-server < 4.3.2`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.