CVE-2026-4270

AWS API MCP File Access Restriction Bypass

Published Mar 16, 2026 CVSS 4.0 · 6.8 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-2cpp-j2fc-qhp7 AWS API MCP File Access Restriction Bypass
History
Type Values Removed Values Added
First Time appeared Amazon
Amazon aws Api Mcp Server
CPEs cpe:2.3:a:amazon:aws_api_mcp_server:*:*:*:*:*:python:*:*
Vendors & Products Amazon
Amazon aws Api Mcp Server
Type Values Removed Values Added
First Time appeared Aws
Aws aws Api Mcp Server
Vendors & Products Aws
Aws aws Api Mcp Server
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title AWS API MCP File Access Restriction Bypass
Weaknesses CWE-424
References
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N'}

cvssV4_0

{'score': 6.8, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
AMZN
Published
Updated
Mar 16, 2026, 6:17 PM
Reserved
Mar 16, 2026, 2:28 PM
Status
Analyzed
Published
Mar 16, 2026, 5:16 PM
Modified
Jun 17, 2026, 10:56 AM