Is CVE-2025-53366 actively exploited?

No active exploitation of CVE-2025-53366 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2025-53366 be exploited remotely?

Yes. CVE-2025-53366 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2025-53366?

CVE-2025-53366 has a CVSS score of 8.7 (HIGH).

HOME VULNERABILITIESCVE-2025-53366

HIGH

CVE-2025-53366

CWE-248Published: July 4, 2025· Updated: Jun 17, 2026

8.7

CVSS v3.1

Official Description

The MCP Python SDK, called `mcp` on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to version 1.9.4, a validation error in the MCP SDK can cause an unhandled exception when processing malformed requests, resulting in service unavailability (500 errors) until manually restarted. Impact may vary depending on the deployment conditions, and presence of infrastructure-level resilience measures. Version 1.9.4 contains a patch for the issue.

NVD Source

Technical Analysis

CVE-2025-53366 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

CVSS v3.1 Vector Breakdown

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges Req.None

User InteractionNone

ScopeX

Impact

Confidentiality

Integrity

Availability

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X