# RUSTSEC-2026-0461 - Unbounded tool schema cache in Streamable HTTP server transport

Source: https://junglewise.ai/threats/rustsec-2026-0461-unbounded-tool-schema-cache-in-streamable-http-server-35418a7a  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-20  
License: CC BY 4.0 with a link back

Severity: low · CVSS 3.1 · Published 2026-10-20

Unbounded tool schema cache in Streamable HTTP server transport

Technologies: [rmcp (crates.io)](https://junglewise.ai/threats/technologies/rmcp). Vendors: [crates.io](https://junglewise.ai/threats/vendors/crates-io).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Low severity, with a CVSS score of 3.1, published 20 October 2026.

**Which products and versions are affected?** rmcp (crates.io) SEMVER:introduced=3.0.0,fixed=3.6.0.

**Is there a fix for This vulnerability?** Yes. rmcp (crates.io): upgrade to 3.6.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected?** Check whether you run rmcp (crates.io) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- rmcp (crates.io): upgrade to 3.6.0 or later

  ```sh
  cargo update -p rmcp
  ```


## Affected products

- rmcp (crates.io) SEMVER:introduced=3.0.0,fixed=3.6.0

## Identifiers

- GHSA-4432-vg92-fqh6
- RUSTSEC-2026-0461

## Related threats

- [RUSTSEC-2026-0462 - Unbounded response body buffering in Streamable HTTP clients](https://junglewise.ai/threats/rustsec-2026-0462-unbounded-response-body-buffering-in-streamable-http-3cfaf6d0)
- [rmcp OAuth client SSRF via unresolved hostnames](https://junglewise.ai/threats/rustsec-2026-0457-oauth-client-ssrf-filter-checks-host-strings-not-26bba63d)
- [rmcp OAuth client SSRF via server-controlled resource_metadata URL](https://junglewise.ai/threats/rmcp-oauth-client-fetches-server-controlled-resource-metadata-urls-6efc52a6)
- [Model Context Protocol Rust SDK custom header leak on cross-origin redirects](https://junglewise.ai/threats/cve-2026-64684-model-context-protocol-rust-sdk-custom-header-leak-on-cross)
- [RMCP Streamable HTTP server unauthenticated session-table memory leak](https://junglewise.ai/threats/cve-2026-63128-rmcp-streamable-http-server-unauthenticated-session-table-memory)