Skip to main content
VulnerabilityPublished Updated

Rmcp: Unbounded tool schema cache

Affects rmcpSource GCVE Database

0

CVSS 7.5 High : upgrade to 3.6.0 soon.

Data as of 9 Nov 2026, 11:32 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 3.6.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

What to do

Upgrade rmcp to 3.6.0.

Affected software

ProductAffectedFixed in
crates.iormcppkg:cargo/rmcpOther threatsAffected
  • >=3.0.0 <3.6.0
Fixed in
  • 3.6.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in rmcp version 3.6.0, which removes the unbounded cache. Users should upgrade to 3.6.0 or later. If upgrading is not possible, deploy authentication in front of the Streamable HTTP server transport endpoint to restrict access or reject tools/call requests with unknown tool names before they reach the vulnerable service.

Description

The rmcp Streamable HTTP server transport versions 3.0.0 through 3.5.x have an unbounded cache of tool schema results keyed by tool name. This cache grows with each incoming tools/call request, including those rejected with HTTP 400, potentially leading to memory exhaustion. The vulnerability affects servers using protocol version 2026-07-28 or later and lacking authentication in front of the endpoint. The issue was fixed in version 3.6.0 by removing the cache and calling ServerHandler::get_tool on each request. Mitigation includes upgrading to 3.6.0 or implementing authentication or request filtering to block unknown tool names.

References

Community reviews

Loading reviews…