AI Sec Watch: A Security Intelligence Platform for AI Systems

Luu, T.J.

HighVulnerability

GHSA-89xv-2j6f-qhc8: Cross-Site Tool Execution for HTTP Servers without Authorizatrion in github.com/modelcontextprotocol/go-sdk

Source: GitHub Advisory(opens in a new tab)
Identifiers: CVE-2026-33252GHSA-89xv-2j6f-qhc8
Published: March 19, 2026
Record updated: October 10, 2026

View JSON

Affected: github.com/modelcontextprotocol/go-sdk <= 1.4.0
Fixed in: 1.4.1
Known exploitation: Not listed in the CISA Known Exploited Vulnerabilities catalog at the last check.
EPSS: 0.2%

Summary

The Go SDK for MCP (github.com/modelcontextprotocol/go-sdk) had a flaw in its Streamable HTTP transport. It accepted browser-generated cross-site POST requests without validating the Origin header or requiring Content-Type: application/json. Without Authorization configured, especially in stateless or sessionless setups, any website could send MCP requests to a local server and potentially trigger tool execution. Cross-site POSTs with Content-Type: text/plain could reach message handling without a CORS preflight barrier.

Mitigation

Fixed in v1.4.1, which adds Content-Type header validation for POST requests and a configurable origin verification protection (commit a433a83). Note: v1.4.1 requires Go 1.25 or later.

Details

Scores and exploitation

CVSS score: 7.1(high)
Patch available: Yes
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:L
Attack vector: network
Attack complexity: low
Privileges required: none
User interaction: required
EPSS: 0.2%Estimated probability that this CVE is exploited in the next 30 days, from the FIRST Exploit Prediction Scoring System. Read on October 10, 2026.
Disclosure date: March 19, 2026

Weaknesses and techniques

Weakness (CWE): CWE-352

Affected

Packages: github.com/modelcontextprotocol/go-sdk@<= 1.4.0 (fixed: 1.4.1)

Classification

Attack type: Other
Attack sophistication: Trivial
AI component targeted: API
Impact: Confidentiality,
Integrity
Labels: security

How this record was produced

Summaries, mitigations and labels on this page are generated automatically from the source. The linked source is authoritative.

Original source: https://github.com/advisories/GHSA-89xv-2j6f-qhc8

First tracked: October 10, 2026 at 12:52 AM ET, from GitHub Advisory Database

Classifier: claude-haiku-5-5, prompt v4

Classifier confidence: 90% (self-assessed)

Affected packages in the Exposure Registry

Matched by package name and ecosystem. Each entry shows whether the package delegates to a language model and how many tracked packages depend on it.

github.com/modelcontextprotocol/go-sdkGoLLM dependency since 2025-07-01 · 1 tracked dependent

Topics

Model Context Protocol

Summary

Mitigation

Affected packages in the Exposure Registry

Topics

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