Java-SDK has a DNS Rebinding Vulnerability
Summary
The java-sdk contains a DNS rebinding vulnerability. This vulnerability allows an attacker to access a locally or network-private java-sdk MCP server via a victims browser that is either local, or network adjacent.
This allows an attacker to make any tool call to the server as if they were a locally running MCP connected AI agent.
Details
Prior to 1.0.0 no Origin header validation was occurring, in violation of the MCP specification. Base Protocol > Transports: 2.0.1 Security Warning:
1: Servers MUST validate the Origin header on all incoming connections to prevent DNS rebinding attacks.
When the web server serving HTTP traffic to the MCP server does not perform standard CORS checks, a DNS rebinding attack is possible.
Some default server configurations and frameworks come with embedded Origin header validation. MCP servers built using those are not vulnerable to this issue. For example, the following are NOT vulnerable:
- Spring AI
Impact
Any developer connecting to a malicious website can inadvertently allow an attacker to make tool calls to local or private-network MCP servers.
Workarounds
Users can mitigate this risk by:
- Running the MCP server behind a reverse proxy (like Nginx or HAProxy) configured to strictly validate the
HostandOriginheaders. - Using a framework that inherently enforces strict CORS and Origin validation (such as Spring AI).
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | io.modelcontextprotocol.sdk:mcp-core | < 1.0.0 | 1.0.0 |
References
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N- Weakness (CWE)
CWE-346- Platform
- Java / Kotlin (Maven)
- Package
io.modelcontextprotocol.sdk:mcp-core- Disclosed
- 07.04.2026
- Updated
- 11.10.2026 13:20
Sources and licenses
OSV / GitHub Advisory Database - GHSA-8jxr-pr72-r468 - CC BY 4.0
Vulnerability history: io.modelcontextprotocol.sdk:mcp-core
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 03.2026 04.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 1
Disclosures per year
- 2026: 2
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Java-SDK has a DNS Rebinding Vulnerability this entry
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