Java-SDK has a DNS Rebinding Vulnerability

Answer in brief

CVE-2026-35568 records a Unknown severity vulnerability in Java-SDK has a DNS Rebinding Vulnerability. The current sources do not mark it as known exploited. The current feed maps io.modelcontextprotocol.sdk:mcp-core (maven). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Apr 7, 2026Updated Sep 10, 2026Source checked Sep 10, 2026First seen by HOL Aug 7, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps io.modelcontextprotocol.sdk:mcp-core (maven). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
io.modelcontextprotocol.sdk:mcp-coremaven	>=0 <1.0.0	1.0.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for io.modelcontextprotocol.sdk:mcp-core.
Review the reported fix. Update io.modelcontextprotocol.sdk:mcp-core to 1.0.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Apr 7, 2026
Evidence: source:osv:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:record
First seen by HOL
Aug 7, 2026

Sources and claim methodology

Upstream source description

### 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](https://modelcontextprotocol.io/specification/2025-06-18/basic/transports#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).

Quoted source text, attributed separately from HOL analysis.