CVE-2026-63127

8.2 HIGH 0.2% exploit odds Fix listed Other Library

What it is

RMCP is an official Rust SDK for the Model Context Protocol. Prior to 2.0.0, the rmcp crate's OAuth implementation in crates/rmcp/src/transport/auth.rs omits the RFC 9728 resource field from ResourceServerMetadata and allows discover_oauth_server_via_resource_metadata to use protected-resource metadata without confirming that the returned resource identifier exactly matches the configured MCP server. A malicious MCP server can publish metadata for a different legitimate MCP resource and its authorization server, causing a victim who connects and completes the authorization flow to obtain a legitimate access token that the client subsequently sends to the malicious server. The attacker can capture the token and impersonate the victim against the legitimate MCP resource within the token's granted scopes. This issue is fixed in version 2.0.0.

At a glance

Exploitability: Can be exploited over the network without logging in, but needs a user to act. High risk of data exposure.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-07-15 16:54 UTC ReservedThe CVE id was reserved by its CNA
2026-09-16 15:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-09-30 17:51 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.2% in the next 30 days (EPSS).
Severity: 8.2 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-09-16 15:17 UTC
Last modified: 2026-09-30 17:51 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-345
Record status: Deferred

Attack profile CVSS 3.1 · 8.2

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: Required
Scope: Changed
Confidentiality: High
Integrity: Low
Availability: None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-63127.md and follow it. Check whether this project is affected by CVE-2026-63127. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

· More options · Status badge

Download Square Reddit

Fix and advisories

References

NVD record · CVE.org record