CVE-2026-55604Disclosure

LOWCVSS 8.6 · HIGH

Exploit discussion active in current signal (1 latest mentions)

Immediate actions

Patch affected systems immediately
Hunt for exploitation attempts and persistence artifacts

Recommended action window: High priority (within 72h)

NVD description

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.

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2.5/ 10 priority

Sources & remediation

Other references

Weakness type (CWE)

CWE-639

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

AVAILABLE

Momentum

NONE

Threat summary

Exploit tooling references are present in monitored signal
Patch or workaround signal is available
1 mentions across 1 observed day

What's happening

Exploit tool or code specified in 1 signal
Patch or workaround mentioned in 1 signal
Technical details provided in 1 signal
Disclosure: 1 classified signal
1 total mentions across 1 day

Deep dive

Activity timeline1 mentions / 1d

Signal classification1 categories

Disclosure

1100.0%

Full discourse1 post

Upwind Security MDR@UpwindMDR93d
Disclosure
🚨High - DeepSeek MCP Server Session Hijack via User-Controlled session_id (CVE-2026-55604) DeepSeek MCP Server's 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 the deepseek_sessions tool, then reuse a victim's session_id in deepseek_chat. That lets the attacker retrieve and continue another user's conversation context - reading their chat history and hijacking the session. It's an IDOR/authorization-bypass (CWE-639) with high confidentiality impact, most dangerous in shared multi-user MCP deployments. 👉Upgrade DeepSeek MCP Server to 1.7.0.
Post summary
The post announces the discovery of a session hijacking vulnerability (CVE-2026-55604) in DeepSeek MCP Server, details its exploitation technique via session ID enumeration, and advises users to upgrade to version 1.7.0 to mitigate the issue.
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