Session Management Flaw in DeepSeek MCP Server Affects Multiple Versions
CVE-2026-55604

8.6HIGH

Key Information:

Vendor

Arikusi

Status
Deepseek-mcp-server
Vendor
CVE Published:
9 July 2026

What is CVE-2026-55604?

The DeepSeek MCP Server, prevalent from version 1.4.2 up to 1.7.0, suffers from a serious flaw where the SessionStore freely accepts unverified session_id values. This loophole enables attackers to enumerate valid session IDs through the deepseek_sessions endpoint. By exploiting this vulnerability, an attacker can hijack an ongoing conversation by injecting a previously captured session ID into the deepseek_chat interface, thereby gaining unauthorized access to a victim’s interaction without any form of authentication. Version 1.7.0 has been updated to address this issue.

Affected Version(s)

deepseek-mcp-server >= 1.4.2, < 1.7.0

References

https://github.com/arikusi/deepseek-mcp-server/security/a...
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https://github.com/arikusi/deepseek-mcp-server/releases/t...
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CVSS V3.1

Score:
8.6
Severity:
HIGH
Confidentiality:
High
Integrity:
Low
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.