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TI-2026-45065 Aliases CVE-2026-63127GHSA-33f5-2c5q-wgwj

RMCP: Missing Resource Field Validation in OAuth Protected Resource Metadata Discovery

Priority HIGH 69CWE-345Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
High · Low · None
Fix status
Partial Red Hat: 2 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-345.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00195 9th percentileScored 2026-11-07
Fix Partial rust-sdk (modelcontextprotocol): 2.0.0rmcp (crates.io): 2.0.0Red Hat: 2 advisoriesRed Hat: 2 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MLflowrust-sdkbefore 2.0.02.0.0Patch availableCNA
—rmcp (crates.io)before 2.0.02.0.0Patch availableGHSA-33f5-2c5q-wgwj
  • rust-sdk VendorMLflow Affected before 2.0.0 Fixed in 2.0.0 Patch available CNA
  • rmcp (crates.io) Vendor— Affected before 2.0.0 Fixed in 2.0.0 Patch available GHSA-33f5-2c5q-wgwj

Remediation

  • Fix · CNA rust-sdk (modelcontextprotocol) Fixed in 2.0.0
  • Fix · GHSA-33f5-2c5q-wgwj rmcp (crates.io) Fixed in 2.0.0 Advisory →

Red Hat 2 advisories

  • RHSA-2026:80765 Released 2026-10-12 · Red Hat rating Important
    goose security update
    • Red Hat Enterprise Linux Extensions Channel (v. 10) goose-1.45.0-1.el10_2
  • RHSA-2026:80764 Released 2026-10-12 · Red Hat rating Important
    goose security update
    • Red Hat Enterprise Linux Extensions Channel (v. 9) goose-1.45.0-1.el9_8

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 10AffectedNo fix yet
Red Hat Enterprise Linux 9AffectedNo fix yet

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-63127
  2. 2026-10-03 Alias added: GHSA-33f5-2c5q-wgwj
  3. 2026-10-12 Fix available: RHSA-2026:80765 · Red Hat
  4. 2026-10-12 Fix available: RHSA-2026:80764 · Red Hat

References

Advisory 1

Other 5

  • TI-2026-46366 Server-side request forgery in mlflow KEVCVSS 3.1CRITICAL 9.3
  • TI-2023-03518 Absolute Path Traversal in mlflow/mlflow CVSS 3.1CRITICAL 10.0
  • TI-2023-01113 Path Traversal: '\..\filename' in mlflow/mlflow CVSS 3.1CRITICAL 9.8
  • TI-2025-31759 Redis Lua Use-After-Free may lead to remote code execution CVSS 3.1CRITICAL 10.0
  • TI-2026-81527 Code execution via scorer deserialization in MLflow servers CVSS 3.1CRITICAL 9.8
  • TI-2025-14028 Command Injection in mlflow/mlflow CVSS 3.1CRITICAL 10.0
See all 175 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences