---
id: "CVE-2026-115845"
kind: "vulnerability"
aliases: ["CVE-2026-115845"]
title: "AWS MCP Server: incomplete Python sandbox validation in run_script tool"
severity: "medium"
cvss: 6.4
epss: 0.0038
exploited: false
status: "open"
category: "ai-tooling"
products: []
ecosystems: []
tags: ["ai-agents", "ai-tooling", "aws", "lab-disclosure", "mcp"]
not_affected_if: ["managed-hosting", "no-aws-mcp-server"]
published_at: "2026-10-23T00:00:00+00:00"
first_seen_at: "2026-10-23T21:57:34+00:00"
updated_at: "2026-10-25T12:38:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-115845", "first_seen_at": "2026-10-23T21:57:34+00:00"}, {"source": "lab", "url": "https://aws.amazon.com/security/security-bulletins/rss/2026-149-aws/", "first_seen_at": "2026-10-24T19:43:42+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-115845", "first_seen_at": "2026-10-25T12:38:50+00:00"}]
---

# AWS MCP Server: incomplete Python sandbox validation in run_script tool

The Python code validator of the run_script tool in AWS MCP Server uses an incomplete list of disallowed inputs. An authenticated user can send a crafted script to execute arbitrary code inside their own isolated session.

_Summary, check and fix written by a model from the sources; labelled as such._

## Fix

- No customer action required; AWS has fixed the issue service-side in the managed AWS MCP Server.

## Mitigated for you by

- AWS (platform-fix): covers The run_script Python code validator in the AWS MCP Server managed service, addressed service-side for all customers. Limits: None stated. Still: None required according to the bulletin. https://aws.amazon.com/security/security-bulletins/rss/2026-149-aws/

## Timeline

- 2026-10-23T21:57:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-115845
- 2026-10-24T19:43:42+00:00 lab https://aws.amazon.com/security/security-bulletins/rss/2026-149-aws/ — AWS: CVE-2026-115845 - Incomplete validation in the run_script Python sandbox in AWS MCP Server
- 2026-10-25T12:38:50+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-115845

## Documents

- [advisory] AWS: CVE-2026-115845 - Incomplete validation in the run_script Python sandbox in AWS MCP Server https://aws.amazon.com/security/security-bulletins/rss/2026-149-aws/

## From the sources

CVE-2026-115845 - Incomplete validation in the run_script Python sandbox in AWS MCP Server

### CVE-2026-115845 - Incomplete validation in the run_script Python sandbox in AWS MCP Server

Bulletin ID: 2026-149-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 10/23/2026 12:00 PM PDT

Description:

AWS MCP Server is a managed server that gives AI agents access to AWS through the Model Context Protocol (MCP), including a run_script tool that runs Python scripts in a sandboxed environment.

We identified CVE-2026-115845, an issue in the Python code validator of the run_script tool in AWS MCP Server. An incomplete list of disallowed inputs might allow an authenticated remote user to execute arbitrary code within their own isolated session environment via a crafted script.

Impacted versions: N/A (managed service, exclusively hosted)

Resolution:

This issue has been addressed service-side. No customer action is required.

Workarounds:

The run_script tool is designed to orchestrate AWS APIs through a Python script. If you use it only to run a Python script that makes AWS API calls, no workaround is required.

References:

- CVE-2026-115845

Acknowledgement:

We would like to thank Manash Saikiafor collaborating on this issue through the coordinated vulnerability disclosure process.

 Please email aws-security@amazon.com with any security questions or concerns.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_