### Summary **Hardcoded Wildcard CORS (Access-Control-Allow-Origin: * )** - https://github.com/modelcontextprotocol/java-sdk/blob/main/mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletSseServerTransportProvider.java#L289 - https://github.com/modelcontextprotocol/java-sdk/blob/main/mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletStreamableServerTransportProvider.java#L525 ### Attack Scenario An attacker-controlled web page instructs the victim's browser to open GET https://internal-mcp-server/sse. Because Access-Control-Allow-Origin: * allows cross-origin SSE reads, the attacker's page receives the endpoint event — which contains the session ID. The attacker can then POST to that endpoint from their page using the victim's browser as a relay. ### Comparison with python-sdk No Access-Control-Allow-Origin header is emitted by either Python transport. The browser's default same-origin policy remains in full effect. https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/sse.py https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/streamable_http.py ### Recommendation In the SDK, the transport layer should not own CORS policy. Server implementors who need cross-origin access can add a CORS filter at the servlet filter or Spring Security layer. ### Reference - https://cheatsheetseries.owasp.org/cheatsheets/HTTP_Headers_Cheat_Sheet.html#access-control-allow-origin
### Summary **Hardcoded Wildcard CORS (Access-Control-Allow-Origin: * )** - https://github.com/modelcontextprotocol/java-sdk/blob/main/mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletSseServerTransportProvider.java#L289 - https://github.com/modelcontextprotocol/java-sdk/blob/main/mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletStreamableServerTransportProvider.java#L525 ### Attack Scenario An attacker-controlled web page instructs the victim's browser to open GET https://internal-mcp-server/sse. Because Access-Control-Allow-Origin: * allows cross-origin SSE reads, the attacker's page receives the endpoint event — which contains the session ID. The attacker can then POST to that endpoint from their page using the victim's browser as a relay. ### Comparison with python-sdk No Access-Control-Allow-Origin header is emitted by either Python transport. The browser's default same-origin policy remains in full effect. https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/sse.py https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/streamable_http.py ### Recommendation In the SDK, the transport layer should not own CORS policy. Server implementors who need cross-origin access can add a CORS filter at the servlet filter or Spring Security layer. ### Reference - https://cheatsheetseries.owasp.org/cheatsheets/HTTP_Headers_Cheat_Sheet.html#access-control-allow-origin
Update io.modelcontextprotocol.sdk:mcp-core to 1.1.1; io.modelcontextprotocol.sdk:mcp-core to 1.0.1; io.modelcontextprotocol.sdk:mcp-core to 0.18.3 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanMCP Java SDK has a Hardcoded Wildcard CORS (Access-Control-Allow-Origin: *) affects io.modelcontextprotocol.sdk:mcp-core (maven), io.modelcontextprotocol.sdk:mcp-core (maven), io.modelcontextprotocol.sdk:mcp-core (maven). Severity is medium. ### Summary **Hardcoded Wildcard CORS (Access-Control-Allow-Origin: * )** - https://github.com/modelcontextprotocol/java-sdk/blob/main/mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletSseServerTransportProvider.java#L289 - https://github.com/modelcontextprotocol/java-sdk/blob/main/mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletStreamableServerTransportProvider.java#L525 ### Attack Scenario An attacker-controlled web page instructs the victim's browser to open GET https://internal-mcp-server/sse. Because Access-Control-Allow-Origin: * allows cross-origin SSE reads, the attacker's page receives the endpoint event — which contains the session ID. The attacker can then POST to that endpoint from their page using the victim's browser as a relay. ### Comparison with python-sdk No Access-Control-Allow-Origin header is emitted by either Python transport. The browser's default same-origin policy remains in full effect. https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/sse.py https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/streamable_http.py ### Recommendation In the SDK, the transport layer should not own CORS policy. Server implementors who need cross-origin access can add a CORS filter at the servlet filter or Spring Security layer. ### Reference - https://cheatsheetseries.owasp.org/cheatsheets/HTTP_Headers_Cheat_Sheet.html#access-control-allow-origin
AI coding agents often install or upgrade packages automatically in maven. A medium vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| io.modelcontextprotocol.sdk:mcp-coremaven | =1.1.0 | 1.1.1 |
| io.modelcontextprotocol.sdk:mcp-coremaven | =1.0.0 | 1.0.1 |
| io.modelcontextprotocol.sdk:mcp-coremaven | <0.18.3 | 0.18.3 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL GuardUpdate io.modelcontextprotocol.sdk:mcp-core to 1.1.1; io.modelcontextprotocol.sdk:mcp-core to 1.0.1; io.modelcontextprotocol.sdk:mcp-core to 0.18.3 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanMCP Java SDK has a Hardcoded Wildcard CORS (Access-Control-Allow-Origin: *) affects io.modelcontextprotocol.sdk:mcp-core (maven), io.modelcontextprotocol.sdk:mcp-core (maven), io.modelcontextprotocol.sdk:mcp-core (maven). Severity is medium. ### Summary **Hardcoded Wildcard CORS (Access-Control-Allow-Origin: * )** - https://github.com/modelcontextprotocol/java-sdk/blob/main/mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletSseServerTransportProvider.java#L289 - https://github.com/modelcontextprotocol/java-sdk/blob/main/mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletStreamableServerTransportProvider.java#L525 ### Attack Scenario An attacker-controlled web page instructs the victim's browser to open GET https://internal-mcp-server/sse. Because Access-Control-Allow-Origin: * allows cross-origin SSE reads, the attacker's page receives the endpoint event — which contains the session ID. The attacker can then POST to that endpoint from their page using the victim's browser as a relay. ### Comparison with python-sdk No Access-Control-Allow-Origin header is emitted by either Python transport. The browser's default same-origin policy remains in full effect. https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/sse.py https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/streamable_http.py ### Recommendation In the SDK, the transport layer should not own CORS policy. Server implementors who need cross-origin access can add a CORS filter at the servlet filter or Spring Security layer. ### Reference - https://cheatsheetseries.owasp.org/cheatsheets/HTTP_Headers_Cheat_Sheet.html#access-control-allow-origin
AI coding agents often install or upgrade packages automatically in maven. A medium vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| io.modelcontextprotocol.sdk:mcp-coremaven | =1.1.0 | 1.1.1 |
| io.modelcontextprotocol.sdk:mcp-coremaven | =1.0.0 | 1.0.1 |
| io.modelcontextprotocol.sdk:mcp-coremaven | <0.18.3 | 0.18.3 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL Guard