# CVE-2026-4270: AWS API MCP File Access Restriction Bypass

> CVE-2026-4270: AWS API MCP File Access Restriction Bypass. CVSS 5.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-4270
Last updated: 2026-06-17T10:56:20Z

- Published: 2026-03-16 16:07 UTC · Updated: 2026-06-17 10:56 UTC · Assigner: AMZN
- CVSS: 5.5 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
- EPSS: 0.13%, 3th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-424

## 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 vendors and products

- AWS: AWS API MCP Server

## Tracked companies

- [Amazon Web Services](https://rewindex.com/company/aws.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-4270)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-4270)
- [https://aws.amazon.com/security/security-bulletins/2026-007-AWS/](https://aws.amazon.com/security/security-bulletins/2026-007-AWS/)
- [https://pypi.org/project/awslabs.aws-api-mcp-server/1.3.9/](https://pypi.org/project/awslabs.aws-api-mcp-server/1.3.9/)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-4270 · Markdown: https://rewindex.com/cve/CVE-2026-4270.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-4270 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:14:41.029Z