CVE-2026-4270: CWE-424: Improper Protection of Alternate Path in AWS AWS API MCP Server
Bulletin ID: 2026-007-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 2026/03/16 09:15 AM PDT Description: The AWS API MCP Server is an open source Model Context Protocol (MCP) server that enables AI assistants to interact with AWS services and resources through AWS CLI commands. It provides programmatic access to manage your AWS infrastructure while maintaining proper security controls. This server acts as a bridge between AI assistants and AWS services, allowing you to create, update, and manage AWS resources across all available services. The server includes a configurable file access feature that controls how AWS CLI commands interact with the local file system. By default, file operations are restricted to a designated working directory (workdir), but this can be configured to allow unrestricted file system access (unrestricted) or to block all local file path arguments entirely (no-access). We identified CVE-2026-4270: Improper Protection of Alternate Path exists in the no-access and workdir feature of the AWS API MCP Server versions >= 0.2.14 and = 0.2.14, < 1.3.9 Please refer to the article below for the most up-to-date and complete information related to this AWS Security Bulletin.
AI Analysis
Technical Summary
This vulnerability (CVE-2026-4270) affects AWS API MCP Server versions 0.2.14 through before 1.3.9. It is caused by improper protection of an alternate path related to the no-access and workdir feature, allowing attackers to bypass file access restrictions and read arbitrary local files within the MCP client application context. The issue impacts confidentiality but does not compromise data integrity or system availability. The CVSS 3.1 base score is 5.5, reflecting medium severity with local attack vector, low complexity, no privileges required, and user interaction needed.
Potential Impact
An attacker with local access and the ability to interact with the MCP client application could potentially bypass intended file access restrictions and read arbitrary local files, leading to confidentiality breaches. There is no impact on system availability or data integrity. No known exploits have been observed in the wild.
Mitigation Recommendations
Users should upgrade AWS API MCP Server to version 1.3 or later, where this vulnerability is fixed. Since this is not a cloud service, remediation depends on user action to apply the update. Patch status is confirmed by the vendor advisory recommending upgrading to version 1.3.
CVE-2026-4270: CWE-424: Improper Protection of Alternate Path in AWS AWS API MCP Server
Description
Bulletin ID: 2026-007-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 2026/03/16 09:15 AM PDT Description: The AWS API MCP Server is an open source Model Context Protocol (MCP) server that enables AI assistants to interact with AWS services and resources through AWS CLI commands. It provides programmatic access to manage your AWS infrastructure while maintaining proper security controls. This server acts as a bridge between AI assistants and AWS services, allowing you to create, update, and manage AWS resources across all available services. The server includes a configurable file access feature that controls how AWS CLI commands interact with the local file system. By default, file operations are restricted to a designated working directory (workdir), but this can be configured to allow unrestricted file system access (unrestricted) or to block all local file path arguments entirely (no-access). We identified CVE-2026-4270: Improper Protection of Alternate Path exists in the no-access and workdir feature of the AWS API MCP Server versions >= 0.2.14 and = 0.2.14, < 1.3.9 Please refer to the article below for the most up-to-date and complete information related to this AWS Security Bulletin.
CVSS v3.1
Score 5.5medium
Affected software
AWS
AWS API MCP Server
pkg:pypi/awslabs-aws-api-mcp-serverRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability (CVE-2026-4270) affects AWS API MCP Server versions 0.2.14 through before 1.3.9. It is caused by improper protection of an alternate path related to the no-access and workdir feature, allowing attackers to bypass file access restrictions and read arbitrary local files within the MCP client application context. The issue impacts confidentiality but does not compromise data integrity or system availability. The CVSS 3.1 base score is 5.5, reflecting medium severity with local attack vector, low complexity, no privileges required, and user interaction needed.
Potential Impact
An attacker with local access and the ability to interact with the MCP client application could potentially bypass intended file access restrictions and read arbitrary local files, leading to confidentiality breaches. There is no impact on system availability or data integrity. No known exploits have been observed in the wild.
Mitigation Recommendations
Users should upgrade AWS API MCP Server to version 1.3 or later, where this vulnerability is fixed. Since this is not a cloud service, remediation depends on user action to apply the update. Patch status is confirmed by the vendor advisory recommending upgrading to version 1.3.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- AMZN
- Date Reserved
- 2026-03-16T14:28:58.998Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 69b8316f9d4df4518370fea8
Added to database: 03/16/2026, 16:35:59 UTC
Last enriched: 06/05/2026, 19:29:50 UTC
Last updated: 09/14/2026, 10:01:31 UTC
Views: 227
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