CVE-2026-63128
Description
A flaw was found in rmcp, a Rust SDK for the Model Context Protocol. An unauthenticated remote attacker can send specially crafted JSON-RPC POST requests to the stateful Streamable HTTP server. These requests cause the server to create and permanently retain session and channel state without proper validation. Repeated exploitation of this vulnerability can lead to unbounded growth of the session table, resource exhaustion, and ultimately a Denial of Service (DoS) for the server.
Statement
Important: This flaw allows an unauthenticated remote attacker to cause a denial of service by exhausting server memory and resources. The rmcp Rust SDK, when used to implement a stateful Streamable HTTP server, is susceptible to resource exhaustion due to improper session management, which can impact legitimate client latency and terminate the server process.
Mitigation
To mitigate this issue, restrict network access to the service utilizing the `rmcp` Streamable HTTP server to trusted clients only. Implement firewall rules to limit inbound connections to the specific port and IP addresses where the vulnerable service is exposed.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (Other); DoS: Resource Consumption (Memory); DoS: Resource Consumption (CPU)
An attacker that can influence the allocation of resources that are not properly released could deplete the available resource pool and prevent all other processes from accessing the same type of resource. Frequently-affected resources include memory, CPU, disk space, power or battery, etc.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
