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CVE-2026-35568

MCP Java-SDK has a DNS Rebinding Vulnerability

7.6 HighFix available

MCP Java SDK is the official Java SDK for Model Context Protocol servers and clients. Prior to 1.0.0, 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. This vulnerability is fixed in 1.0.0.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
Passive

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

0.14%Up 0.1 points since Apr 8, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.6

MCP Java-SDK has a DNS Rebinding Vulnerability

MCP Java SDK is the official Java SDK for Model Context Protocol servers and clients. Prior to 1.0.0, 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. This vulnerability is fixed in 1.0.0.

Record
CVE-2026-35568
CVSS 4.0
7.6 HighCVSS: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-346
Updated
2026-11-02
EUVDEUVD-2026-19954 7.6

MCP Java SDK is the official Java SDK for Model Context Protocol servers and clients. Prior to 1.0.0, 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. This vulnerability is fixed in 1.0.0.

Record
EUVD-2026-19954
CVSS 4.0
7.6 HighCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-8jxr-pr72-r468 7.6

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:

  1. Running the MCP server behind a reverse proxy (like Nginx or HAProxy) configured to strictly validate the Host and Origin headers.
  2. Using a framework that inherently enforces strict CORS and Origin validation (such as Spring AI).
Record
GHSA-8jxr-pr72-r468
CVSS 4.0
7.6 HighCVSS: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-346
Updated
2026-11-02
NVD 7.6

MCP Java SDK is the official Java SDK for Model Context Protocol servers and clients. Prior to 1.0.0, 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. This vulnerability is fixed in 1.0.0.

Record
CVE-2026-35568
CVSS 4.0
7.6 HighCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
5.7 MediumCVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Weakness
CWE-346
Updated
2026-11-02
OSV 7.6

MCP Java-SDK has a DNS Rebinding Vulnerability

MCP Java SDK is the official Java SDK for Model Context Protocol servers and clients. Prior to 1.0.0, 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. This vulnerability is fixed in 1.0.0.

Record
CVE-2026-35568
CVSS 4.0
7.6 HighCVSS: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-346
Updated
2026-11-02
OSVGHSA-8jxr-pr72-r468 7.6

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:

  1. Running the MCP server behind a reverse proxy (like Nginx or HAProxy) configured to strictly validate the Host and Origin headers.
  2. Using a framework that inherently enforces strict CORS and Origin validation (such as Spring AI).
Record
GHSA-8jxr-pr72-r468
CVSS 4.0
7.6 HighCVSS: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-346
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
io.modelcontextprotocol.sdk:mcp-core
Maven
 before 1.0.0
1.0.0
io.modelcontextprotocol.sdk:mcp-core
Maven
 before 1.0.0, plus listed versions
0.13.00.13.10.14.00.14.10.15.0
Show 10 moreShow less
0.16.00.17.00.17.10.17.20.18.00.18.10.18.20.18.30.18.41.0.0-RC3
1.0.0

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-35568 is a high vulnerability (CVSS 7.6) in Lfprojects Mcp Java Sdk, published April 7, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.14%, the 3rd percentile. Fixed in io.modelcontextprotocol.sdk:mcp-core 1.0.0.

References

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