modelcontextprotocol python-sdk up to 1.29.x/2.1.x streamable_http_client redirect

Summaryinfo

A vulnerability was found in modelcontextprotocol python-sdk up to 1.29.x/2.1.x and classified as problematic. This affects an unknown part of the component streamable_http_client. Such manipulation leads to redirect. This vulnerability is referenced as CVE-2026-116685. It is possible to launch the attack remotely. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in modelcontextprotocol python-sdk up to 1.29.x/2.1.x and classified as problematic. Affected by this issue is an unknown code of the component streamable_http_client. The manipulation with an unknown input leads to a redirect vulnerability. Using CWE to declare the problem leads to CWE-601. A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks. Impacted is integrity. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-116685 since 10/26/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1204.001 by the MITRE ATT&CK project.

Upgrading to version 1.30.0 or 2.2.0 eliminates this vulnerability.

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Productinfo

Type

• Programming Language Software

Vendor

• modelcontextprotocol

Name

• python-sdk

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 1.22
• 1.23
• 1.24
• 1.25
• 1.26
• 1.27
• 1.28
• 1.29
• 2.0
• 2.1

Website

• Product: https://github.com/modelcontextprotocol/python-sdk/

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CPE 2.2info

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