DEV Community

CVE Reports
CVE Reports

Posted on Originally published at cvereports.com

CVE-2026-55604: CVE-2026-55604: Authorization Bypass via Global Session Singleton in @arikusi/deepseek-mcp-server

#security #cve #cybersecurity

CVE-2026-55604: Authorization Bypass via Global Session Singleton in @arikusi/deepseek-mcp-server

Vulnerability ID: CVE-2026-55604
CVSS Score: 8.6
Published: 2026-08-25

An Authorization Bypass Through User-Controlled Key (CWE-639 / Insecure Direct Object Reference) vulnerability exists in @arikusi/deepseek-mcp-server starting in version 1.4.2 and fixed in 1.7.0. In Streamable HTTP transport mode, a process-global SessionStore singleton allows any remote client to retrieve or modify active conversation contexts belonging to other clients.

TL;DR

A global session singleton allows unauthenticated remote attackers to list, read, and manipulate all active multi-turn LLM chat contexts when running in HTTP transport mode.

⚠️ Exploit Status: POC

Technical Details

  • CWE ID: CWE-639
  • Attack Vector: Network
  • CVSS Score: 8.6
  • EPSS Score: 0.00372 (Percentile: 29.99%)
  • Impact: Complete Context Disclosure / Data Exfiltration
  • Exploit Status: Proof of Concept Available
  • CISA KEV Status: Not Listed

Affected Systems

  • @arikusi/deepseek-mcp-server >= 1.4.2, < 1.7.0
  • @arikusi/deepseek-mcp-server: >= 1.4.2 < 1.7.0 (Fixed in: 1.7.0)

Code Analysis

Commit: 9fd5142

Fix: Refactor SessionStore to remove singleton and scope it per transport connection

Exploit Details

Mitigation Strategies

  • Upgrade the @arikusi/deepseek-mcp-server package to version 1.7.0 or higher.
  • Disable the Streamable HTTP transport mode if not strictly required, relying instead on single-tenant STDIO.
  • Implement network-level access controls and authentication proxies if HTTP transport is mandatory.

Remediation Steps:

  1. Identify all deployments of @arikusi/deepseek-mcp-server.
  2. Check the package version in package.json and verify if TRANSPORT=http is defined in environment variables.
  3. Execute npm install @arikusi/deepseek-mcp-server@1.7.0 to apply the patch.
  4. Restart the MCP server process and verify that session isolation is successfully enforced.

References

Read the full report for CVE-2026-55604 on our website for more details including interactive diagrams and full exploit analysis.

Top comments (0)