What is CVE-2025-6515?

CVE-2025-6515 is a medium-severity vulnerability in Oatpp Oatpp-Mcp, classified under Use of Insufficiently Random Values. CVSS score: 6.8/10. Published 2025-10-20.

How severe is CVE-2025-6515?

Medium severity. CVSS v3 base score is 6.8 out of 10.

Vulnerability in Oatpp Oatpp-Mcp

CVE-2025-6515

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.

EPSS: 0.004 (30.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:H.

Affected products

Oatpp Oatpp-mcp — versions 0

Weakness classification (CWE)

CWE-330 — Use of Insufficiently Random Values

References

reefs@jfrog.com (third-party-advisory)

Frequently asked questions

What is CVE-2025-6515?: CVE-2025-6515 is a medium-severity vulnerability in Oatpp Oatpp-Mcp, classified under Use of Insufficiently Random Values. CVSS score: 6.8/10. Published 2025-10-20.
How severe is CVE-2025-6515?: Medium severity. CVSS v3 base score is 6.8 out of 10.