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dynoxide: DNS rebinding and cross-origin CSRF via MCP HTTP transport

High severity GitHub Reviewed Published May 11, 2026 in nubo-db/dynoxide

Package

npm dynoxide (npm)

Affected versions

>= 0.9.3, < 0.9.13

Patched versions

0.9.13
cargo dynoxide-rs (Rust)
>= 0.9.3, < 0.9.13
0.9.13

Description

Summary

dynoxide's MCP HTTP transport was vulnerable to DNS rebinding via its transitive rmcp dependency, plus a related cross-origin CSRF gap. A malicious web page could make the user's browser send requests to a local dynoxide mcp --http or dynoxide serve --mcp server with a non-loopback Host header, which the server would then process. Affects 0.9.3 to 0.9.12. The stdio transport (dynoxide mcp without --http, which is the default) is not affected.

Impact

If a user is running dynoxide mcp --http (or dynoxide serve --mcp) on their machine and then visits a malicious web page, the attacker's JavaScript can call any MCP tool exposed by the running dynoxide instance.

Reachable tools include reads (get_item, query, scan, batch_get_item, describe_table, list_tables) and writes (put_item, update_item, delete_item, create_table, batch_write_item).

Any data in tables that the local dynoxide instance has access to can be read, modified, or destroyed.

Patches

dynoxide 0.9.13 closes both the named CVE and a related cross-origin CSRF gap:

  1. DNS rebinding (the named CVE). rmcp is upgraded from 1.1.1 to 1.6.0. rmcp 1.4+ ships a default Host-header allowlist (["localhost", "127.0.0.1", "::1"]) which rejects requests carrying any other Host header with a 403.

  2. Defence in depth. Explicit allowed_hosts and allowed_origins lists are now set on StreamableHttpServerConfig directly. The Host allowlist protects against a future rmcp default flip. The Origin allowlist closes a related cross-origin CSRF gap that the Host check alone does not address: a malicious page could fetch the loopback endpoint with mode: 'no-cors', the Host header would match (it's the literal loopback address the browser is connecting to), but the Origin header would otherwise have been unchecked.

Native MCP clients that don't send an Origin header (Claude Code, Cursor, the dynoxide CLI) are unaffected by the Origin check and continue to work.

Workarounds

  • Upgrade to dynoxide 0.9.13.
  • If upgrade is not immediately possible: do not run the MCP HTTP transport. Run dynoxide mcp (stdio, the default) instead of dynoxide mcp --http, and don't pass --mcp to dynoxide serve.

Resources

Credits

Vulnerability identified via GitHub Dependabot alert on the transitive rmcp dependency.

References

@hicksy hicksy published to nubo-db/dynoxide May 11, 2026
Published to the GitHub Advisory Database May 18, 2026
Reviewed May 18, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS score

Weaknesses

Origin Validation Error

The product does not properly verify that the source of data or communication is valid. Learn more on MITRE.

Reliance on Reverse DNS Resolution for a Security-Critical Action

The product performs reverse DNS resolution on an IP address to obtain the hostname and make a security decision, but it does not properly ensure that the IP address is truly associated with the hostname. Learn more on MITRE.

Cross-Site Request Forgery (CSRF)

The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor. Learn more on MITRE.

CVE ID

No known CVE

GHSA ID

GHSA-fvh2-gm75-j4j7

Source code

Credits

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