8.1

CVE-2025-66416: lfprojects mcp_python_sdk

CVSS: 8.1v3.1HighAnalyzed
AliasesGHSA-9h52-p55h-vw2fPYSEC-2026-1617CGA-7mmq-hg7p-hjgp
Published 02-12-2025Last modified 02-12-2025
Open JSON

Vulnerability summary

CVE-2025-66416 is a high (CVSS 8.1) vulnerability in lfprojects mcp_python_sdk. EPSS estimates a 0.51% chance of exploitation in the next 30 days, higher than 42.4% of scored vulnerabilities.

Overall risk
33/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.1/10
010
High · v3.1 (NVD)
EPSS score
0.51%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 0 · Related 1
CGA-4RR5-V9CG-V92P

Timeline

  1. 02-12-2025
    PublishedVulnerability first disclosed.
  2. 02-12-2025
    Last modifiedVulnerability information updated.

Description

The MCP Python SDK, called `mcp` on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to version 1.23.0, tThe Model Context Protocol (MCP) Python SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication using FastMCP with streamable HTTP or SSE transport, and has not configured TransportSecuritySettings, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances. Note that running HTTP-based MCP servers locally without authentication is not recommended per MCP security best practices. This issue does not affect servers using stdio transport. This vulnerability is fixed in 1.23.0.

CVSS metrics

6 scores · 5 sources · 2 versions

EPSS trend

Probability

0.51%

Chance of exploitation in the next 30 days

Percentile

42%

Versus all other CVEs

30-day change

0.00 pp

From 0.51% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.51%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Chainguard3 products
  • open-webui-compat< 0.6.40-r1
  • py3-semgrep< 1.145.0-r0
  • semgrep< 1.145.0-r0
Wolfi3 products
  • open-webui-compat< 0.6.40-r1
  • py3-semgrep< 1.145.0-r0
  • semgrep< 1.145.0-r0
Lfprojects1 product
Modelcontextprotocol1 product
PyPI1 product
  • mcp< 1.23.0

5 vendors · 9 products

References

8 links