Vulnerability · Published Oct 20, 2025 · Assigned by JFROG
CVE-2025-6515Reuse of session IDs in oatpp-mcp leads to session hijacking and prompt hijacking by remote attackers
Medium 6.8
In plain English
A medium-severity weak randomness in oatpp-mcp from oatpp. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities).
Severity (CVSS 3.1)6.8Medium
Exploit odds (30 days)0.4%top 65.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official 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.
Affected products (as reported)
Weakness: CWE-330 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:H