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HIGH severity

GHSA-fvh2-gm75-j4j7 — dynoxide-rs

HIGH

GHSA-fvh2-gm75-j4j7 is a high-severity (CVSS 7.5) CWE-346 vulnerability in dynoxide-rs. A fix is available for dynoxide-rs — see the affected versions and patch details below.

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

Also known asCVE-2026-42559GHSA-89vp-x53w-74fxRUSTSEC-2026-0140RUSTSEC-2026-0189
Published
May 18, 2026
Updated
Jun 29, 2026
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Sep 29, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-fvh2-gm75-j4j7.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs14th percentile — riskier than 14% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-fvh2-gm75-j4j7 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 380,526 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected
🦀dynoxide-rs📦dynoxide

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io, npm packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iodynoxide-rs≥ 0.9.3&&< 0.9.130.9.13cargo update -p dynoxide-rs --precise 0.9.13
📦npmdynoxide≥ 0.9.3&&< 0.9.130.9.13npm install dynoxide@0.9.13

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for dynoxide-rs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update dynoxide-rs to 0.9.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fvh2-gm75-j4j7 is resolved across your whole dependency graph.

  3. Workarounds

    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.

Frequently Asked Questions

## 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 w
O3 Security · Impact-Aware SCA

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GHSA-fvh2-gm75-j4j7: dynoxide-rs (High 7.5) | O3 Security