CVE-2026-1166855.9MediumCWE-200

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

modelcontextprotocol · python-sdk

Affected: modelcontextprotocol python-sdk · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.4%probability of exploitation in the next 30 days

34th percentile

050100

Higher than 34% of scored CVEs

5.9MediumCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

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.

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

modelcontextprotocol · python-sdk>= 1.8.0, < 1.30.0; >= 2.0.0, < 2.2.0

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

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Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Information Exposure · Information Disclosure
Vendor: modelcontextprotocol
Published: October 2026
Band: Unlikely (under 1%), October 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-116685 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.