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Critical @modelcontextprotocol/server SDK flaw exposes client data

A critical vulnerability, CVE-2026-111770, has been identified in the @modelcontextprotocol/server SDK, affecting versions 2.0.0 through 2.2.0. The flaw allows one client to receive another client's responses or notifications when sharing the same HTTP MCP server instance. This race condition occurs because messages are matched by JSON-RPC ID alone, which can collide when multiple clients start requests from zero. The issue, rated High severity with a CVSS score of 7.7, was fixed in version 2.3.0 and is attributed to developers DavidCarliez and legitu1337. AI

IMPACT This vulnerability highlights the risks of shared state in server SDKs, potentially impacting developers relying on the MCP protocol for AI agent communication.

RANK_REASON Security vulnerability disclosure for a specific SDK.

Read on dev.to — MCP tag →

AI-generated summary · Google Gemini · from 1 sources. How we write summaries →

Critical @modelcontextprotocol/server SDK flaw exposes client data

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0 / 100
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Tool
Security vulnerability disclosure for a specific SDK.
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Only one publisher covered this so far. Single-source stories can still rank when the publisher is high-authority, but they lack cross-source corroboration.
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product, safety
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High
Clearly on-topic for AI-industry coverage.
Story freshness
3 days old
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Full methodology in our editorial standards.

COVERAGE [1]

  1. dev.to — MCP tag TIER_1 English(EN) · Actionable Vectors ·

    Whose response is this? The MCP server SDK that matched replies by id alone

    <h1> Whose response is this? The MCP server SDK that matched replies by id alone </h1> <p><em>A vector breakdown of CVE-2026-111770 / GHSA-jm63-cq47-j5jp (<code>@modelcontextprotocol/server</code> 2.0.0 through 2.2.0, fixed in 2.3.0)</em></p> <p>No injection, no stolen token. Two…