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CVE-2026-4270— AWS API MCP File Access Restriction Bypass

Quick assessment

Affected
AWS AWS API MCP Server
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Amazon Web Services API MCP Server是Amazon Web Services开源的一个大模型上下文服务器。 Amazon Web Services API MCP Server 0.2.14至1.3.9之前版本存在安全漏洞，该漏洞源于对备用路径的保护不当，可能导致绕过预期的文件访问限制，并在MCP客户端应用环境中暴露任意本地文件内容。

CVSS 5.5 · Medium EPSS 0.18% · P7
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I. Basic Information for CVE-2026-4270

Vulnerability Information
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Vulnerability Title
AWS API MCP File Access Restriction Bypass
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对候选路径的不恰当保护
Source: CVE Program / CVE List V5
Vulnerability Title
Amazon Web Services API MCP Server 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Amazon Web Services API MCP Server是Amazon Web Services开源的一个大模型上下文服务器。 Amazon Web Services API MCP Server 0.2.14至1.3.9之前版本存在安全漏洞，该漏洞源于对备用路径的保护不当，可能导致绕过预期的文件访问限制，并在MCP客户端应用环境中暴露任意本地文件内容。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
AWS AWS API MCP Server 0.2.14 ~ 1.3.9 -

II. Public POCs for CVE-2026-4270

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III. Intelligence Information for CVE-2026-4270

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Vendor Advisories for CVE-2026-4270 (1)

Vendor Pages for CVE-2026-4270 (1)

IV. Related Vulnerabilities

Same vendor: AWS
Same weakness: CWE-424

V. Comments for CVE-2026-4270

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