AWS API MCP File Access Restriction Bypass
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).
Description: Improper Protection of Alternate Path exists in the no-access and workdir feature of the AWS API MCP Server versions >= 0.2.14 and < 1.3.9 on all platforms may allow the bypass of intended file access restriction and expose arbitrary local file contents in the MCP client application context.
To remediate this issue, users should upgrade to version 1.3.9.
This issue can be reached with local access to the system, attack complexity is low, an attacker needs no privileges on the target. A user must be tricked into taking some action. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity none, availability none.
The score comes from this vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
CVE-2026-4270 is classified as CWE-424: Improper Protection of Alternate Path. The product does not sufficiently protect all possible paths that a user can take to access restricted functionality or resources.
CVE-2026-4270 is recorded against 2 packages.
Published on 16 March 2026 and last revised on 17 June 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.
These advisories are the same class of weakness (CWE-424: Improper Protection of Alternate Path) in other software:
Details
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Affected Packages
| Software | From version | Fixed in |
|---|---|---|
| aws-api-mcp-server | 0.2.14 | 1.3.9 |
| awslabs-aws-api-mcp-server | 0.2.14 | 1.3.9 |
References
Vulnerability Monitoring
CVE-2026-4270 is rated CVSS 5.5 Medium. BotEraser monitors your WordPress installation and notifies you when software you use appears in our vulnerability database.
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