Vulnerability record/PUBLISHED/Published Oct 27, 2026 19:26:46 UTC

CVE-2026-116685

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.

Base score5.9/ 10

SeverityMediumCVSS 3.1

Exploitability / impact

CVSS metric breakdown

Vector-derived attributes

Base severityMedium

Attack vectorNetworkAV

Attack complexityHighAC

Privileges requiredNonePR

User interactionNoneUI

ScopeUnchangedS

Confidentiality impactHighC

Integrity impactNoneI

Availability impactNoneA

CVSS vector stringCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS communicates standardized severity and impact characteristics. It does not establish whether a system is exploitable in your specific environment.

Record context

CVE Numbering AuthorityGitHub_M

Last updatedOct 27, 2026 19:26:46 UTC

PublishedOct 27, 2026 19:26:46 UTC

ReservedOct 26, 2026 20:00:59 UTC