# CVE-2025-53365: Model Context Protocol Python SDK denial of service in HTTP transport

Source: https://junglewise.ai/threats/cve-2025-53365-model-context-protocol-python-sdk-denial-of-service-in-http  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-07-04. Updated: 2026-07-16  
License: CC BY 4.0 with a link back

CVE-2025-53365 · Severity: high · CVSS 4 · Published 2025-07-04

The Model Context Protocol (MCP) Python SDK contains a flaw that allows a remote user to crash the server. By establishing a specific type of web connection and then triggering an error, an attacker can force the server to shut down unexpectedly. This results in a denial of service, requiring a manual restart to restore operations.

Technologies: [Anthropic Model Context Protocol](https://junglewise.ai/threats/technologies/model-context-protocol), [mcp (PyPI)](https://junglewise.ai/threats/technologies/pypi-mcp). Vendors: [Anthropic](https://junglewise.ai/threats/vendors/anthropic), [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2025-53365 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-53365 being exploited in the wild.

**How severe is CVE-2025-53365?** High severity, with a CVSS score of 4, published 4 July 2025.

**Which products and versions are affected?** Anthropic Model Context Protocol < 1.10.0; mcp (PyPI) ECOSYSTEM:introduced=0,fixed=1.10.0.

**Is there a fix for CVE-2025-53365?** Yes. mcp (PyPI): upgrade to 1.10.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2025-53365 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2025-53365?** Check whether you run Anthropic Model Context Protocol or mcp (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- mcp (PyPI): upgrade to 1.10.0 or later

  ```sh
  pip install "mcp>=1.10.0"
  ```


## Technical details

An unhandled exception vulnerability (CWE-248) exists in the MCP Python SDK's streamable HTTP transport component. If a client establishes a streamable HTTP session and subsequently triggers an exception, the server fails to catch a 'ClosedResourceError'. This uncaught exception leads to a process crash. The attack can be carried out over the network without prior authentication or user interaction. A fix is available in version 1.10.0, which implements proper exception handling for these transport sessions.

## Affected products

- Model Context Protocol mcp < 1.10.0

## Identifiers

- CVE-2025-53365
- GHSA-j975-95f5-7wqh
- PYSEC-2026-1618

## Timeline

- 2025-07-04: disclosed
- 2025-07-04: advisory
- 2025-07-04: patched: Version 1.10.0 released

## References

- [https://api.github.com/users/rharang](https://api.github.com/users/rharang)
- [https://github.com/rharang](https://github.com/rharang)
- [https://api.github.com/users/rharang/gists%7B/gist_id%7D](https://api.github.com/users/rharang/gists%7B/gist_id%7D)
- [https://api.github.com/users/rharang/repos](https://api.github.com/users/rharang/repos)
- [https://avatars.githubusercontent.com/u/8082617?v=4](https://avatars.githubusercontent.com/u/8082617?v=4)
- [https://api.github.com/users/rharang/events%7B/privacy%7D](https://api.github.com/users/rharang/events%7B/privacy%7D)

## Related threats

- [Model Context Protocol Python SDK unvalidated $ref fetching](https://junglewise.ai/threats/cve-2026-116686-the-model-context-protocol-python-sdk-is-the-official-python-sdk)
- [Model Context Protocol Python SDK credential and body leak on cross-origin redirects](https://junglewise.ai/threats/cve-2026-116685-the-model-context-protocol-python-sdk-is-the-official-python-sdk)
- [Model Context Protocol Python SDK token resource confusion in bearer authentication](https://junglewise.ai/threats/cve-2026-116684-the-model-context-protocol-python-sdk-is-the-official-python-sdk)
- [MCP Python SDK unbounded session accumulation in StreamableHTTP](https://junglewise.ai/threats/cve-2026-59951-mcp-python-sdk-unbounded-session-accumulation-in-streamablehttp)
- [RMCP Streamable HTTP server unauthenticated session-table memory leak](https://junglewise.ai/threats/cve-2026-63128-rmcp-streamable-http-server-unauthenticated-session-table-memory)