CVE-2026-55604Public exploitNetwork attack vector

Cross-session data exposure via shared SessionStore

Published Jul 9, 2026 · Updated Jul 9, 2026

Authorization bypass in DeepSeek MCP Server 1.4.2 through 1.6.9 allows remote attackers to read and alter other users' sessions over HTTP. The process-global SessionStore indexes its map with caller-supplied session_id values, and deepseek_sessions lists those keys without binding them to an MCP transport session. Exploitation requires HTTP transport and another client's active session in the same process; it exposes conversation history and permits continuation or deletion, while STDIO mode is unaffected.

CVSS severity8.6
High
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization bypass in DeepSeek MCP Server 1.4.2 through 1.6.9 allows remote attackers to read and alter other users' sessions over HTTP. The process-global SessionStore indexes its map with caller-supplied session_id values, and deepseek_sessions lists those keys without binding them to an MCP transport session. Exploitation requires HTTP transport and another client's active session in the same process; it exposes conversation history and permits continuation or deletion, while STDIO mode is unaffected.

The record

CVE
CVE-2026-55604
Published
Jul 9, 2026
Updated
Jul 9, 2026
Vendor
arikusi
Product
DeepSeek MCP Server
Classifications
CWE-639
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 1.4.2, < 1.7.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

arikusi · DeepSeek MCP Serverversion=>= 1.4.2, < 1.7.0

Published CVSS scores

8.6GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-639Authorization Bypass Through User-Controlled Key

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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