CVE-2026-67431: CWE-284: Improper Access Control in modelcontextprotocol ruby-sdk
CVE-2026-67431 is a high-severity vulnerability in the MCP Ruby SDK prior to version 0.23.0. The issue involves improper access control where the StreamableHTTPTransport component does not bind session IDs to session owners. This flaw allows an attacker who has obtained a stolen session ID to send requests that execute within the victim's session context. The vulnerability is fixed in version 0.23.0.
AI Analysis
Technical Summary
The MCP Ruby SDK's StreamableHTTPTransport component (in versions before 0.23.0) fails to bind session IDs to their respective session owners, resulting in improper access control (CWE-284). This allows an attacker with a stolen session ID to execute tools or call requests as the victim, effectively hijacking the session. The vulnerability has a CVSS 4.0 score of 8.3, indicating high severity. The issue is resolved in version 0.23.0 of the SDK.
Potential Impact
An attacker who obtains a valid session ID can impersonate the legitimate user by sending requests that execute within the victim's session. This can lead to unauthorized actions being performed under the victim's identity, potentially compromising confidentiality and integrity of the victim's session data and operations.
Mitigation Recommendations
Upgrade the MCP Ruby SDK to version 0.23.0 or later, where the issue is fixed by properly binding session IDs to session owners. No other mitigation or temporary workaround is indicated in the available data.
CVE-2026-67431: CWE-284: Improper Access Control in modelcontextprotocol ruby-sdk
Description
CVE-2026-67431 is a high-severity vulnerability in the MCP Ruby SDK prior to version 0.23.0. The issue involves improper access control where the StreamableHTTPTransport component does not bind session IDs to session owners. This flaw allows an attacker who has obtained a stolen session ID to send requests that execute within the victim's session context. The vulnerability is fixed in version 0.23.0.
CVSS v4.0
Score 8.3high
Affected software
modelcontextprotocol
ruby-sdk
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The MCP Ruby SDK's StreamableHTTPTransport component (in versions before 0.23.0) fails to bind session IDs to their respective session owners, resulting in improper access control (CWE-284). This allows an attacker with a stolen session ID to execute tools or call requests as the victim, effectively hijacking the session. The vulnerability has a CVSS 4.0 score of 8.3, indicating high severity. The issue is resolved in version 0.23.0 of the SDK.
Potential Impact
An attacker who obtains a valid session ID can impersonate the legitimate user by sending requests that execute within the victim's session. This can lead to unauthorized actions being performed under the victim's identity, potentially compromising confidentiality and integrity of the victim's session data and operations.
Mitigation Recommendations
Upgrade the MCP Ruby SDK to version 0.23.0 or later, where the issue is fixed by properly binding session IDs to session owners. No other mitigation or temporary workaround is indicated in the available data.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-07-29T15:07:24.991Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a6a53159c2644c7f8f0f10c
Added to database: 07/29/2026, 19:23:01 UTC
Last enriched: 08/06/2026, 17:53:54 UTC
Last updated: 09/12/2026, 22:01:36 UTC
Views: 63
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