gcdRadar
archive/Patch now/AIR-2026-0136
closedclosed 16 Sep 2026Patch now2 Disclosed vulnerabilityAI

RMCP Rust SDK Leaks Custom Headers on Cross-Origin Redirects

RMCP, Model Context Protocol

Prior to version 2.1.0, the rmcp crate applied caller-supplied custom headers without marking them sensitive, causing authentication tokens to be replayed upon following redirects. A compromised MCP endpoint can exploit this to capture API keys.

disclosed CVENo confirmed exploitation, so this record is tracked as a disclosed vulnerability and not counted as an incident. It moves into the counts if CISA or the vendor confirms exploitation. Why

CVSS
6.8
EPSS
0.01 · top 57% · 2026-11-13
EPSS scores by FIRST
fix status
Fix status unknown
first report
16 Sep 2026
last update
16 Sep 2026
CVE ids
CVE-2026-64684other records

Timeline · 1

  1. 16 Sep 2026CVE-2026-64684: RMCP is an official Rust SDK for the Model Context Protocol.

Sources · 1

Advisories and databases

  1. 2026-09-16
    CVE-2026-64684: RMCP is an official Rust SDK for the Model Context Protocol.
    NVD · nvd.nist.gov/vuln/detail/CVE-2026-64684

Titles and links belong to their publishers. The summary above is written by gcdRadar in its own words; data is CC BY-SA 4.0.

Classification

lane
Patch now
AI role
Attack on AI
categories
Infrastructure vulnerability
severity
2 · Disclosed vulnerability
fix status
Fix status unknown
targets
Framework / tooling
owasp llm top 10
LLM03:2025 Supply Chain
mitre atlas
no technique for these categories
tags
mcprustsdk
dates
happened 16 Sep 2026 · first reported 16 Sep 2026
origin
NVD
Vulnerability record from NVD / the GitHub Advisory Database. This product uses the NVD API but is not endorsed or certified by the NVD.
record
confidence 0.95 · created 2026-10-18 06:33Z · updated 2026-10-18 06:33Z

Lane, AI role, categories and severity come from the classifier; the OWASP and ATLAS rows are derived from the categories. How these are assigned

Copy a brief

This record as a short Markdown brief, for a ticket, a chat or a coding agent.

the brief as text
# RMCP Rust SDK Leaks Custom Headers on Cross-Origin Redirects

https://gcdradar.vercel.app/incidents/rmcp-rust-sdk-leaks-custom-headers-on-cross-origin-redirects · AIR-2026-0136 · closed 2026-09-16

- Lane: Patch now
- Severity: 2 (Disclosed vulnerability)
- Fix status: Fix status unknown
- First reported: 2026-09-16
- AI role: Attack on AI
- Products: RMCP, Model Context Protocol
- CVE ids: CVE-2026-64684
- CVSS: 6.8

## Summary

Prior to version 2.1.0, the rmcp crate applied caller-supplied custom headers without marking them sensitive, causing authentication tokens to be replayed upon following redirects. A compromised MCP endpoint can exploit this to capture API keys.

## What to do

No action recorded; read the sources below and the vendor's advisory.

## Latest updates

- 2026-09-16: CVE-2026-64684: RMCP is an official Rust SDK for the Model Context Protocol. (https://nvd.nist.gov/vuln/detail/CVE-2026-64684)

## Sources

- 2026-09-16 NVD: CVE-2026-64684: RMCP is an official Rust SDK for the Model Context Protocol. https://nvd.nist.gov/vuln/detail/CVE-2026-64684

Verify against the vendor's advisory before changing production. Data CC BY-SA 4.0, https://gcdradar.vercel.app.

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