Medium 5.5Published Mar 16, 2026

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

Updated under an hour ago (Oct 26, 2026, 5:30 PM ET)

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It affects AWS API MCP Server and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for AWS API MCP Server

Exploited in the last 30 days

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.

CVSS: 5.5 MEDIUM (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Weakness (CWE): CWE-424
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: AMZN
NVD analysis: Analyzed
Record last updated: Mar 16, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

AWS AWS API MCP Server aws:api_mcp_server (from the name)	from 0.2.14 before 1.3.9	CNA record
amazon aws_api_mcp_server amazon:aws_api_mcp_server	from 0.2.14 before 1.3.9	NVD

References

References

https://aws.amazon.com/security/security-bulletins/2026-007-AWS/	vendor-advisory
https://pypi.org/project/awslabs.aws-api-mcp-server/1.3.9/	patch, third-party-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.