CVE-2026-55605
MEDIUMCVE-2026-55605 is a medium-severity (CVSS 5.3) Missing Authentication vulnerability. O3 Security confirms whether CVE-2026-55605 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
@arikusi/deepseek-mcp-server Missing Authentication on Self-Hosted HTTP MCP Endpoint
Description
DeepSeek MCP Server is an MCP server for DeepSeek V4. Starting in version 1.4.2 and prior to version 1.8.0, the self-hosted HTTP transport of @arikusi/deepseek-mcp-server exposes POST /mcp without any authentication: createMcpExpressApp is called without an authProvider and no middleware guards the route, so any network-reachable client can issue an unauthenticated initialize request and obtain a valid MCP session identifier. In reproduced testing against commit 5e1302171e99, an unauthenticated client was able to initialize a session, enumerate tools, and invoke the local deepseek_sessions tool with no credentials. The same unauthenticated session also exposes deepseek_chat, whose handler uses the server-side DEEPSEEK_API_KEY when self-hosted deployments configure one. This issue applies to self-hosted HTTP mode, not the separately documented hosted BYOK endpoint in README.md, which expects an Authorization: Bearer ... header. Upstream self-hosted container assets enable HTTP mode by default (Dockerfile) and publish port 3000 (docker-compose.yml). Version 1.8.0 contains a patch for this issue.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-55605 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-55605 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-55605. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-55605 in your dependencies?
O3 detects CVE-2026-55605 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.