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Fencer Vulns
high 8.6

CVE-2026-55604 json

@arikusi/deepseek-mcp-server has an Authorization Bypass Through User-Controlled Key

published 2026-07-09 4 mo ago modified 2026-10-25 14 d ago also GHSA-fh3r-g96v-f578 , EUVD-2026-42720

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 31%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm @arikusi/deepseek-mcp-server 1.7.0

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.37% chance of exploitation in the next 30 days, higher than 31% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/arikusi/deepseek-mcp-server/security/advisories/GHSA-fh3r-g96v-f578 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
GitHub 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L

Affected packages

ecosystem package affected fixed in
npm @arikusi/deepseek-mcp-server
>=1.4.2, <1.7.0
1.7.0

Affected products

  • arikusi deepseek-mcp-server

Classification

Weakness
  • CWE-639 Authorization Bypass Through User-Controlled Key

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.