What is CVE-2026-4270?

CVE-2026-4270 is a medium-severity vulnerability in Amazon AWS API Mcp Server, classified under CWE-424. CVSS score: 5.5/10. Published 2026-03-16.

How severe is CVE-2026-4270?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Vulnerability in Amazon AWS API Mcp Server

CVE-2026-4270

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.

Published 2026-03-16 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.002 (6.9th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 6.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.001 · newest: 0.002 · change: +0.001

Affected products

Amazon AWS API Mcp Server
AWS API Mcp Server — versions 0.2.14

Weakness classification (CWE)

CWE-424

References

ff89ba41-3aa1-4d27-914a-91399e9639e5 (vendor-advisory, Vendor Advisory)
ff89ba41-3aa1-4d27-914a-91399e9639e5 (Third Party Advisory, patch)

Frequently asked questions

What is CVE-2026-4270?: CVE-2026-4270 is a medium-severity vulnerability in Amazon AWS API Mcp Server, classified under CWE-424. CVSS score: 5.5/10. Published 2026-03-16.
How severe is CVE-2026-4270?: Medium severity. CVSS v3 base score is 5.5 out of 10.