Medium severity · published Mar 16, 2026
CVE-2026-4270
AWS API MCP File Access Restriction Bypass
5.5
CVSS
0.1%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 3% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AA
AWS API MCP Server · AWS
0.2.14 before 1.3.9 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-4270
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-4270
Vendor Advisory
https://aws.amazon.com/security/security-bulletins/2026-007-AWS/
Third Party Advisory
https://pypi.org/project/awslabs.aws-api-mcp-server/1.3.9/
More from AWS API MCP Server
7.8
CVE-2026-115413
AWS API MCP Server OAuth Token Audience Validation Bypass
7.0
CVE-2026-16584
AWS API MCP Server Security Policy Bypass via Startup Failure