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JFSA-2025-001494691 - oatpp-mcp prompt hijacking

CVE-2025-6515 | CVSS 6.8

JFrog Severity:medium

Discovered ByOri Hollanderof the JFrog Security Research Team

Published 20 Oct, 2025 | Last updated 20 Oct, 2025

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

oatpp:oatpp-mcp

(,)

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.

No PoC is supplied for this vulnerability

No mitigations are supplied for this issue

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