CVE-2025-6515 json
Reuse of session IDs in oatpp-mcp leads to session hijacking and prompt hijacking by remote attackers
published 2025-10-20 12 mo ago modified 2026-10-08 31 d ago also EUVD-2025-35077
- cvss
- 6.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 34%
- public exploits
- 0
- none known
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 legitimate client MCP sessions, returning malicious responses from the oatpp-mcp server.
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 12 mo ago
Exploit prediction
0.40% chance of exploitation in the next 30 days, higher than 34% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.8 | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:H |
Affected products
- oatpp oatpp-mcp
Classification
- Weakness
-
- CWE-330 Use of Insufficiently Random Values
References
-
research.jfrog.com
/vulnerabilities/oatpp-mcp-prompt-hijacking-jfsa-2025-001494691/
third-party-advisory
Sources
- CVE List CVE-2025-6515
- NVD CVE-2025-6515
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.