How severe is CVE-2025-6515?

CVE-2025-6515 has a CVSS 3.x base score of 6.8, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability high.

Is CVE-2025-6515 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2025-6515?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-6515 have an EU (EUVD) identifier?

Yes. CVE-2025-6515 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-35077.

When was CVE-2025-6515 published?

CVE-2025-6515 was published on 2025-10-20 and last updated on 2026-06-17.

CVE-2025-6515

CVE-2025-6515 is a medium-severity vulnerability with a CVSS 3.x base score of 6.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-330.

Key facts

Severity: Medium (CVSS 3.x base score 6.8)
EPSS exploit prediction: 0% (26th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-35077
Weakness: CWE-330
Published: 2025-10-20
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2025-6515?: CVE-2025-6515 has a CVSS 3.x base score of 6.8, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability high.
Is CVE-2025-6515 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2025-6515?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-6515 have an EU (EUVD) identifier?: Yes. CVE-2025-6515 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-35077.
When was CVE-2025-6515 published?: CVE-2025-6515 was published on 2025-10-20 and last updated on 2026-06-17.

References

https://research.jfrog.com/vulnerabilities/oatpp-mcp-prompt-hijacking-jfsa-2025-001494691/

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