CVE-2026-116685

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

Published Oct 27, 2026 CVSS 3.1 · 5.9 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-5h93-6whr-6q8j Model Context Protocol Python SDK: HTTP client transports followed cross-origin redirects carrying custom headers and bodies
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Modelcontextprotocol
Modelcontextprotocol python-sdk
Vendors & Products Modelcontextprotocol
Modelcontextprotocol python-sdk
Type Values Removed Values Added
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.
Title Model Context Protocol Python SDK: HTTP client transports followed cross-origin redirects carrying custom headers and bodies
Weaknesses CWE-200
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 30, 2026, 3:03 PM
Reserved
Oct 26, 2026, 8:00 PM
Status
Deferred
Published
Oct 27, 2026, 8:17 PM
Modified
Oct 30, 2026, 4:17 PM
Severity
Moderate
Public date
Oct 27, 2026, 7:26 PM