AIKIDO-2026-959725
mcp is vulnerable to Uncontrolled Resource Consumption
62
Medium Risk
This Affects:
mcpTL;DR
The stdio transports in MCP::Server::Transports::StdioTransport and MCP::Client::Stdio read newline-delimited JSON-RPC frames with IO#gets and no limit argument. A peer that streams bytes without emitting a newline forces gets to accumulate the entire stream in a single Ruby string until the process is OOM-killed. This yields a memory-exhaustion denial of service driven by the stdio peer, and is most impactful when the peer is sandboxed or bytes are bridged from a remote source. The fix caps frame reads with a configurable max_line_bytes and closes the connection on over-limit frames.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and use the stdio transport to read frames from a peer you do not fully trust.
Background info
mcp is vulnerable to Uncontrolled Resource Consumption in versions 0.1.0 - 0.22.0.
How to fix this
Upgrade the mcp library to the patch version.
Are You Affected?
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SOC 2Compliant
ISO 27001Compliant