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Vulnerabilities

Vulnerability · 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.

Published Oct 20, 2025 · catalog updated Oct 20, 2025 · The MCP SSE endpoint

Last checked Nov 4, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2025-6515. EPSS is 0.40%. Act only if a listed version of The MCP SSE endpoint is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (The MCP SSE endpoint).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.40%
Remediation
Vendor / distro source
Affected products
vendor oatpp oatpp-mcp 0

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor oatpp oatpp-mcp 00

How to fix CVE-2025-6515

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2025-6515. EPSS is 0.40%. Act only if a listed version of The MCP SSE endpoint is installed.

Which versions are affected?

Compare what you have installed with oatpp oatpp-mcp 0 0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.40%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 20, 2025 · EUVD

    Detected

    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.

  2. Oct 20, 2025 · EUVD

    Updated

    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.

Sources

  • CVE.orgVulnerability recordCVE-2025-6515

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-6515

    30-day exploitation probability 0.40%

    first.org
  • EUVDVulnerability recordEUVD-2025-35077

    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 ma

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Nov 4, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 4, 2026
  • CVE.orgOct 26, 2026
  • EUVDOct 26, 2026