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Authorization Bypass (IDOR)Weakness · CWE-639

CVE-2026-55604

HIGH · 8.6 CVSS v3.1 Published 2026-07-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 6 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
DeepSeek MCP Server is an MCP server for DeepSeek V4. Starting in version 1.4.2 and prior to version 1.7.0, the process-global `SessionStore` accepts caller-supplied `session_id` values without binding them to any authenticated principal or transport session. An attacker can enumerate active session IDs via `deepseek_sessions`, then reuse a victim-controlled `session_id` in `deepseek_chat` to retrieve and continue the victim's conversation context. Version 1.7.0 contains a patch.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The DeepSeek MCP Server's process-global SessionStore accepts caller-supplied session_id values without binding them to authenticated principals or transport sessions. An attacker can enumerate active sessions via deepseek_sessions and then hijack a victim's conversation context by reusing their session_id in deepseek_chat calls.

MitigationUpgrade to version 1.7.0 or later, which contains the patch to properly bind session IDs to authenticated principals.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify DeepSeek MCP Server version
    Query the installed package or binary for its version string using your package manager (pip show, npm list, or similar) or run the server with a version flag if available
    Affected if The installed version is below 1.7.0 (e.g., 1.6.x, 1.5.x, etc.)
  2. Verify deepseek_sessions method is exposed
    Inspect the server's exposed methods or API endpoints to confirm deepseek_sessions is callable without authentication barriers
    Affected if deepseek_sessions is publicly accessible and returns active session identifiers
  3. Confirm session_id parameter acceptance in deepseek_chat
    Test or inspect the deepseek_chat interface to verify it accepts an arbitrary caller-supplied session_id rather than only using internally-bound session context
    Affected if deepseek_chat accepts any session_id value provided by the caller without validating it against the authenticated principal or transport session
  4. Check for session-to-principal binding mechanism
    Review server configuration or authentication logs to determine whether sessions are bound to authenticated users or transport-level session tokens
    Affected if No binding exists between session_id and authenticated identity; sessions are process-global and accept arbitrary identifiers

You are affected if running DeepSeek MCP Server version below 1.7.0 and the deepseek_sessions and deepseek_chat methods expose session enumeration and accept caller-supplied session_id values without binding to authenticated principals.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to version 1.7.0 or later, which contains the patch to properly bind session IDs to authenticated principals.

Recommended fix High confidence

version 1.7.0

  1. 1. Identify the currently installed version of DeepSeek MCP Server by checking your project's dependencies (e.g., package.json, requirements.txt, or similar).
  2. 2. If the installed version is 1.4.2 or later but earlier than 1.7.0, upgrade to version 1.7.0 using your package manager (e.g., pip install deepseek-mcp-server==1.7.0 or npm install [email protected]).
  3. 3. Verify the upgrade was successful by checking the installed version again.
  4. 4. Test that the deepseek_sessions and deepseek_chat functions work correctly with the updated server, confirming the session binding has been properly implemented.

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-55604 in production — separate from our analysis above.

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What belongs here
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  • Version or environment caveats, and links to real fixes
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