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  4. CVE 2026 116684 model context protocol python sdk server bearer
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Medium ยท CVSS 6.8CVE-2026-116684GHSA-W4FH-QVV9-3V23

Model Context Protocol Python SDK: Server bearer-token authentication accepts tokens issued for a different resource serverCVE-2026-116684

Answer in brief

CVE-2026-116684 records a Medium severity (CVSS 6.8) vulnerability in Model Context Protocol Python SDK: Server bearer-token authentication accepts tokens issued for a different resource server. The current sources do not mark it as known exploited. The current feed maps modelcontextprotocol/python-sdk (generic), mcp (pip), mcp (pip). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 27, 2026Updated Oct 27, 2026Source checked Oct 27, 2026First seen by HOL Oct 27, 2026Material review Oct 27, 2026
Upstream Advisory

Key facts

Risk
Medium ยท CVSS 6.8
Exploitation
Not marked as known exploited
Affected software
3 mapped packages or products
Fix availability
Available

Why this deserves its current priority

CVSS is 6.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps modelcontextprotocol/python-sdk (generic), mcp (pip), mcp (pip). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
modelcontextprotocol/python-sdkgeneric>=1.10.0 <1.30.0 || >=2.0.0 <2.2.01.30.0, 2.2.0
mcppip>=2.0.0,<2.2.02.2.0
mcppip>=1.10.0,<1.30.01.30.0

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for modelcontextprotocol/python-sdk, mcp, mcp.
  2. 2Review the reported fix. Update modelcontextprotocol/python-sdk to 1.30.0; mcp to 2.2.0; mcp to 1.30.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Oct 27, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Oct 27, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Oct 27, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
Upstream source description

The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. From 1.10.0 until 1.30.0 and 2.2.0, server-side bearer authentication configured through AuthSettings with token_verifier accepts a valid token issued for another service when the authorization server serves multiple resources and the TokenVerifier does not independently validate the aud audience. This resource-confusion flaw lets a token holder authenticate to the wrong MCP server and exercise that token's resulting access. This issue is fixed in versions 1.30.0 and 2.2.0.

Quoted source text, attributed separately from HOL analysis.

Related CVEs

  • Model Context Protocol Python SDK: HTTP client transports followed cross-origin redirects carrying custom headers and bodiesSame modelcontextprotocol/python-sdk package
  • Model Context Protocol Python SDK: Client fetched server-chosen $ref URLs while validating tool results against output schemasSame modelcontextprotocol/python-sdk package
  • Asterisk: ARI REST-over-WebSocket read-only bypass allows arbitrary module path load and conditional RCEAlso CWE-863
  • MLflow: Arbitrary file read on unauthenticated MLflow servers via prompt model version sourceSame pip ecosystem
  • MLflow CrewAI autologging records LLM provider API keys in logged trace spansSame pip ecosystem
  • MLflow: Remote code execution on unauthenticated MLflow servers via third-party scorer deserialization importing caller-placed artifact modulesSame pip ecosystem

Record context

Vulnerability class
Tool Poisoning
EPSS
Not reported
CWE IDs
CWE-863
Source
CVE List V5
Source checked
Oct 27, 2026
References
8 linked sources
Open source record