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CVE-2026-116685— Model Context Protocol Python SDK: HTTP client transports followed cross-origin redirects carrying custom headers and bodies

Quick assessment

Affected
modelcontextprotocol python-sdk
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Model Context Protocol（MCP）Python SDK 是 MCP 服务器和客户端的官方 Python 软件开发工具包。在版本 1.8.0 至 1.30.0 以及 2.2.0 之间， 、 、 、 、 以及 等客户端路径默认启用了重定向跟随功能（ ）。该功能允许将请求重定向到不同的源（origin），并会将调用方提供的自定义凭据标头（credential headers）随重定向一并转发；对于 307 或 308 响应，还会转发请求体。若攻击者能够影响受信任端点的重定向目标，则可能窃取这些敏感材料

CVSS 5.9 · Medium

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 2

VendorProduct Version RangeStatus
modelcontextprotocol python-sdk >= 1.8.0, < 1.30.0 affected
>= 2.0.0, < 2.2.0 affected
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I. Basic Information for CVE-2026-116685

Vulnerability Information
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Vulnerability Title
Model Context Protocol Python SDK: HTTP client transports followed cross-origin redirects carrying custom headers and bodies
Source: CVE Program / CVE List V5
Vulnerability Description
The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. From 1.8.0 until 1.30.0 and 2.2.0, streamable_http_client, streamablehttp_client, sse_client, ClientSessionGroup, OAuth, and create_mcp_http_client client paths enable follow_redirects and follow redirects to a different origin, forwarding caller-supplied custom credential headers and, for 307 or 308 responses, the request body. An attacker who can influence a trusted endpoint's redirect destination can receive that material. This issue is fixed in versions 1.30.0 and 2.2.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
信息暴露
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
modelcontextprotocol python-sdk >= 1.8.0, < 1.30.0 -

II. Public POCs for CVE-2026-116685

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III. Intelligence Information for CVE-2026-116685

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Other References for CVE-2026-116685 (1)

Other References for CVE-2026-116685 (5)

Same Patch Batch · modelcontextprotocol · 2026-10-27 · 3 CVEs total

CVE-2026-116684 6.8 MEDIUM Model Context Protocol Python SDK: Server bearer-token authentication accepts tokens issue
CVE-2026-116686 6.5 MEDIUM Model Context Protocol Python SDK: Client fetched server-chosen $ref URLs while validating

IV. Related Vulnerabilities

Same product: python-sdk
Same vendor: modelcontextprotocol
Same weakness: CWE-200