Vulnerability · Published Mar 16, 2026 · Assigned by AMZN
CVE-2026-4270AWS API MCP File Access Restriction Bypass
Medium 5.5
In plain English
A medium-severity security flaw in AWS API MCP Server from AWS. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 3% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | awslabs-aws-api-mcp-server | 1.3.9 | GHSA-2cpp-j2fc-qhp7 |
| PyPI | awslabs-aws-api-mcp-server | 1.3.9 | GHSA-2cpp-j2fc-qhp7 |
| PyPI | awslabs-aws-api-mcp-server | 1.3.9 | PYSEC-2026-162 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| AWS | AWS API MCP Server | 0.2.14 – before 1.3.9 |
Weakness: CWE-424 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N