{"id":"CVE-2025-6515","title":"The MCP SSE endpoint in oatpp-mcp returns an instance pointer as the session ID, which is not unique nor cryptographically secure","summary":"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 l…","severity":"medium","cvss":6.8,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:H","cwe":["CWE-330"],"published":"2025-10-20","updated":"2026-10-08","sourceUpdated":"2026-10-08T22:10:00.563","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-6515","references":[{"url":"https://research.jfrog.com/vulnerabilities/oatpp-mcp-prompt-hijacking-jfsa-2025-001494691/","label":"reefs@jfrog.com"}],"tags":["nvd"],"epss":0.00401,"epssPercentile":0.32257,"ingestedAt":"2026-10-08T22:11:53.818Z","slug":"CVE-2025-6515","body":"## Overview\n\nThe 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":37,"depthScoreParts":{"impact":37.4,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}