CVE-2026-4270: Awslabs.aws api mcp server AWS API MCP File Access Vulnerability
MODERATECVE-2026-4270 is a MODERATE (CVSS 5.5) aws api mcp file access vulnerability (CWE-424: Improper Protection of Alternate Path) affecting Awslabs.aws api mcp server libraries in the PyPI ecosystem. The issue involves aws api mcp file access restriction bypass. Remediation is available by upgrading affected packages to version 1.3.9.
CVE-2026-4270 at a Glance
Security Impact
CVSS: 5.5
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N).
How to Fix CVE-2026-4270
To remediate this vulnerability, upgrade all affected Awslabs.aws api mcp server dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
pip install awslabs.aws-api-mcp-server>=1.3.9pip install awslabs-aws-api-mcp-server>=1.3.9Run the following command in your project directory to verify that all resolved dependencies use the patched release:
pip show awslabs.aws-api-mcp-serverHow to Check if You Are Affected
To determine whether your Python environment is affected by CVE-2026-4270, inspect your installed packages using pip:
pip show awslabs.aws-api-mcp-serverAnalyze the terminal output to locate any version of Awslabs.aws api mcp server in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.3.9), your application is affected.
Note: The pip show awslabs.aws-api-mcp-server command checks currently installed packages in your active Python environment.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-424: Improper Protection of Alternate Path, where the product does not sufficiently protect all possible paths that a user can take to access restricted functionality or resources. In Awslabs.aws api mcp server, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-4270 Affected Awslabs.aws api mcp server Versions
2 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
awslabs.aws-api-mcp-server
|
PyPI |
≥ 0.2.14
< 1.3.9
|
1.3.9
|
|
awslabs-aws-api-mcp-server
|
PyPI |
≥ 0.2.14
< 1.3.9
|
1.3.9
|
References
Frequently Asked Questions
What is CVE-2026-4270?
Which Awslabs.aws api mcp server versions are affected?
What version fixes CVE-2026-4270?
Is awslabs.aws-api-mcp-server affected?
Is awslabs-aws-api-mcp-server affected?
What is the CVSS score of CVE-2026-4270?
What CWE is associated with CVE-2026-4270?
How can I check PyPI dependencies for CVE-2026-4270?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-2cpp-j2fc-qhp7",
"modified" : "2026-06-08T23:15:15Z",
"published" : "2026-03-17T20:33:15Z",
"aliases" : [ "CVE-2026-4270" ],
"summary" : "AWS API MCP File Access Restriction Bypass",
"details" : "### Description\n\nThe 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.\n\nThis 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).\n\n**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.\n\nTo remediate this issue, users should upgrade to version 1.3.9.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N"
}, {
"type" : "CVSS_V4",
"score" : "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "PyPI",
"name" : "awslabs.aws-api-mcp-server"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0.2.14"
}, {
"fixed" : "1.3.9"
} ]
} ]
}, {
"package" : {
"ecosystem" : "PyPI",
"name" : "awslabs-aws-api-mcp-server"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0.2.14"
}, {
"fixed" : "1.3.9"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/awslabs/mcp/security/advisories/GHSA-2cpp-j2fc-qhp7"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-4270"
}, {
"type" : "WEB",
"url" : "https://aws.amazon.com/security/security-bulletins/2026-007-AWS"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/awslabs/mcp"
}, {
"type" : "WEB",
"url" : "https://github.com/pypa/advisory-database/tree/main/vulns/awslabs-aws-api-mcp-server/PYSEC-2026-162.yaml"
}, {
"type" : "WEB",
"url" : "https://pypi.org/project/awslabs.aws-api-mcp-server/1.3.9"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-424" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-03-17T20:33:15Z",
"nvd_published_at" : "2026-03-16T17:16:32Z"
}
}