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CVE-2026-4270

AWS API MCP File Access Restriction Bypass

6.8 MediumFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
Low
Privileges needed
None
User interaction
Passive

What an attacker can affect

Confidentiality
High
Integrity
None
Availability
None

Exploit likelihood

0.14%Up 0.1 points since Mar 17, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.8

AWS API MCP File Access Restriction Bypass

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.

Record
CVE-2026-4270
CVSS 4.0
6.8 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Weakness
CWE-424
Updated
2026-11-02
EUVDEUVD-2026-12474 6.8

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.

Record
EUVD-2026-12474
CVSS 4.0
6.8 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-2cpp-j2fc-qhp7 6.8

AWS API MCP File Access Restriction Bypass

Description

The AWS API MCP Server is an open source Model Context Protocol (MCP) server that enables AI assistants to interact with AWS services and resources through AWS CLI commands. It provides programmatic access to manage your AWS infrastructure while maintaining proper security controls.

This server acts as a bridge between AI assistants and AWS services, allowing you to create, update, and manage AWS resources across all available services. The server includes a configurable file access feature that controls how AWS CLI commands interact with the local file system. By default, file operations are restricted to a designated working directory (workdir), but this can be configured to allow unrestricted file system access (unrestricted) or to block all local file path arguments entirely (no-access).

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.

Record
GHSA-2cpp-j2fc-qhp7
CVSS 4.0
6.8 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Weakness
CWE-424
Updated
2026-11-02
NVD 6.8

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.

Record
CVE-2026-4270
CVSS 4.0
6.8 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Weakness
CWE-424
Updated
2026-11-02
OSVGHSA-2cpp-j2fc-qhp7 6.8

AWS API MCP File Access Restriction Bypass

Description

The AWS API MCP Server is an open source Model Context Protocol (MCP) server that enables AI assistants to interact with AWS services and resources through AWS CLI commands. It provides programmatic access to manage your AWS infrastructure while maintaining proper security controls.

This server acts as a bridge between AI assistants and AWS services, allowing you to create, update, and manage AWS resources across all available services. The server includes a configurable file access feature that controls how AWS CLI commands interact with the local file system. By default, file operations are restricted to a designated working directory (workdir), but this can be configured to allow unrestricted file system access (unrestricted) or to block all local file path arguments entirely (no-access).

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.

Record
GHSA-2cpp-j2fc-qhp7
CVSS 4.0
6.8 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Weakness
CWE-424
Updated
2026-11-02
OSVPYSEC-2026-162 6.8

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.

Record
PYSEC-2026-162
CVSS 4.0
6.8 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
awslabs-aws-api-mcp-server
PyPI
 0.2.14 up to 1.3.9
1.3.9
awslabs-aws-api-mcp-server
PyPI
 0.2.14 up to 1.3.9, plus listed versions
0.3.00.3.10.3.20.3.30.3.4
Show 25 moreShow less
1.0.01.0.11.0.21.1.01.1.11.1.21.1.31.1.41.1.51.1.61.1.71.1.81.2.01.2.11.2.21.2.31.3.01.3.11.3.21.3.31.3.41.3.51.3.61.3.71.3.8
1.3.9

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-4270 is a medium vulnerability (CVSS 6.8) in Amazon Aws Api Mcp Server, published March 16, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.14%, the 3rd percentile. Fixed in awslabs-aws-api-mcp-server 1.3.9.

References

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