# CVE-2026-76893: tsParticles: A single anonymous MCP session can monopolize HTTP mode and deny new clients

Status: published. Published: 2026-11-04. Updated: 2026-11-06.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- tsparticles / tsparticles: < 4.3.2 (affected). Source: CNA: GitHub_M
- @tsparticles / mcp-server: < 4.3.2 (affected). Source: CNA: GitHub_M
-  / @tsparticles/mcp-server (@tsparticles/mcp-server): <= 4.3.1 (affected, GitHub advisory range). Source: GitHub GHSA-h7c4-q426-7jh9

## Severity and prioritization

- CVSS 4.0: 6.9 (medium); 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; source: CNA: GitHub_M

- CVSS 4.0: 6.9 (medium); 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: security-advisories@github.com

- CISA KEV: No listing in collected sources

- EPSS: 0.29% as of 2026-11-05; percentile 21.84%

- SSVC: exploitation poc; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-400

## Exploit evidence

- exploit: https://github.com/tsparticles/tsparticles/security/advisories/GHSA-h7c4-q426-7jh9 (ADP: CISA-ADP)

## References

- https://github.com/tsparticles/tsparticles/security/advisories/GHSA-h7c4-q426-7jh9 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/tsparticles/tsparticles/pull/5888 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/tsparticles/tsparticles/commit/d3b5672bd61bb847abfa21193c34eabf7aba6896 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/tsparticles/tsparticles/security/advisories/GHSA-h7c4-q426-7jh9 (ADP: CISA-ADP; exploit)

- https://github.com/tsparticles/tsparticles/commit/d3b5672bd61bb847abfa21193c34eabf7aba6896 (security-advisories@github.com)

- https://github.com/tsparticles/tsparticles/pull/5888 (security-advisories@github.com)

- https://github.com/tsparticles/tsparticles/security/advisories/GHSA-h7c4-q426-7jh9 (security-advisories@github.com)

- https://github.com/tsparticles/tsparticles/security/advisories/GHSA-h7c4-q426-7jh9 (134c704f-9b21-4f2e-91b3-4a467353bcc0)

- https://github.com/tsparticles/tsparticles/security/advisories/GHSA-h7c4-q426-7jh9 (GitHub Security Advisories; advisory)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-76893; retrieved 2026-11-05; source updated 2026-11-05

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76893; retrieved 2026-11-07; source updated 2026-11-06

- GitHub Security Advisories: https://github.com/tsparticles/tsparticles/security/advisories/GHSA-h7c4-q426-7jh9; retrieved 2026-11-06; source updated 2026-08-20

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-76893; retrieved 2026-11-05; source updated Not reported

Revision: b0adba0cbb12ba15c349558288b144ae018d34830537d68f373f8ae46de3f54e

Canonical: https://y2.dev/cve/CVE-2026-76893

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.