CVE-2025-6515
Reuse of session IDs in oatpp-mcp leads to session hijacking and prompt hijacking by remote attackers
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.
INFO
Published Date :
Oct. 20, 2025, 5:15 p.m.
Last Modified :
Oct. 21, 2025, 7:31 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2025-6515
vulnerability.
Even if cvefeed.io
is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
---|---|---|---|---|---|---|
CVSS 3.1 | MEDIUM | 48a46f29-ae42-4e1d-90dd-c1676c1e5e6d | ||||
CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Implement a secure random number generator for session IDs.
- Ensure session IDs are not predictable or sequential.
- Validate session IDs on the server-side.
- Invalidate sessions upon logout or timeout.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-6515
.
URL | Resource |
---|---|
https://research.jfrog.com/vulnerabilities/oatpp-mcp-prompt-hijacking-jfsa-2025-001494691/ |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-6515
is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-6515
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2025-6515
vulnerability anywhere in the article.

-
The Hacker News
ThreatsDay Bulletin: $176M Crypto Fine, Hacking Formula 1, Chromium Vulns, AI Hijack & More
Criminals don’t need to be clever all the time; they just follow the easiest path in: trick users, exploit stale components, or abuse trusted systems like OAuth and package registries. If your stack o ... Read more

-
The Register
MCP attack abuses predictable session IDs to hijack AI agents
A security flaw in the Oat++ implementation of Anthropic's Model Context Protocol (MCP) allows attackers to predict or capture session IDs from active AI conversations, hijack MCP sessions, and inject ... Read more
The following table lists the changes that have been made to the
CVE-2025-6515
vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Oct. 20, 2025
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:H Added CWE CWE-330 Added Reference https://research.jfrog.com/vulnerabilities/oatpp-mcp-prompt-hijacking-jfsa-2025-001494691/