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archive/Patch now/AIR-2026-1221
closedclosed 29 Jul 2026Patch now2 Disclosed vulnerabilityAI

CVE-2026-67431: Session Hijacking Vulnerability in MCP Ruby SDK

mcp gem

A session ownership validation flaw in the MCP Ruby SDK allows attackers with a stolen session identifier to execute tools within a victim's session. The issue was addressed in version 0.23.0.

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
8.3
EPSS
<0.01 · top 70% · 2026-11-13
EPSS scores by FIRST
fix status
Fix status unknown
first report
29 Jul 2026
last update
29 Jul 2026
CVE ids
CVE-2026-67431other records

Timeline · 1

  1. 29 Jul 2026CVE-2026-67431: MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients.

Sources · 1

Advisories and databases

  1. 2026-07-29
    CVE-2026-67431: MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients.
    NVD · nvd.nist.gov/vuln/detail/CVE-2026-67431

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
mcpsession-hijacking
dates
happened 29 Jul 2026 · first reported 29 Jul 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 10:04Z · updated 2026-10-18 10:04Z

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
# CVE-2026-67431: Session Hijacking Vulnerability in MCP Ruby SDK

https://gcdradar.vercel.app/incidents/cve-2026-67431-session-hijacking-vulnerability-in-mcp-ruby-s · AIR-2026-1221 · closed 2026-07-29

- Lane: Patch now
- Severity: 2 (Disclosed vulnerability)
- Fix status: Fix status unknown
- First reported: 2026-07-29
- AI role: Attack on AI
- Products: mcp gem
- CVE ids: CVE-2026-67431
- CVSS: 8.3

## Summary

A session ownership validation flaw in the MCP Ruby SDK allows attackers with a stolen session identifier to execute tools within a victim's session. The issue was addressed in version 0.23.0.

## What to do

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

## Latest updates

- 2026-07-29: CVE-2026-67431: MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. (https://nvd.nist.gov/vuln/detail/CVE-2026-67431)

## Sources

- 2026-07-29 NVD: CVE-2026-67431: MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. https://nvd.nist.gov/vuln/detail/CVE-2026-67431

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

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