AIKIDO-2026-107635
mcp-core is vulnerable to Denial of Service (DoS)
65
Medium Risk
This Affects:
mcp-coreTL;DR
The HTTP client transports parse Server-Sent Events through a shared component that accumulates every data: line into an unbounded StringBuilder and only flushes the event on a blank line. A connected server that sends endless data lines without the SSE terminator causes unbounded heap growth in the client process, leading to OutOfMemoryError or severe garbage-collection pressure. The fix caps SSE line and event sizes and bounds the HTTP response body read on the client transports.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and you use the HTTP client transports to connect to an untrusted MCP server.
Background info
mcp-core is vulnerable to Denial of Service (DoS) in versions 0.18.0 - 0.18.3, 1.0.0 - 1.1.3 and 2.0.0 - 2.0.0.
How to fix this
Upgrade the mcp-core and/or the io.modelcontextprotocol.sdk:mcp-core library to the patch version.
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SOC 2Compliant
ISO 27001Compliant