CVE-2025-6515 MEDIUM

CVE-2025-6515: Reuse of session IDs in oatpp-mcp leads to session hijacking and prompt hijacking by remote attackers

Vendor Oatpp
Product oatpp-mcp
Weakness CWE-330 · Insufficient randomness
Published October 20, 2025
Last update October 20, 2025
View on NVD All CVEs

CVSS base score

6.8/10
Attack vector Network
Attack complexity High
Privileges required None
User interaction Required
Confidentiality None
Integrity High

CVSS vector

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

What the vulnerability does

01Description

The MCP SSE endpoint in oatpp-mcp returns an instance pointer as the session ID, which is not unique nor cryptographically secure. This allows network attackers with access to the oatpp-mcp server to guess future session IDs and hijack legitimate client MCP sessions, returning malicious responses from the oatpp-mcp server.

Key dates

02Disclosure timeline

October 20, 2025 CVE published
October 20, 2025 Record updated