AWS API MCP File Access Restriction Bypass

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Summary

CVECVE-2026-4270
StatePUBLISHED
AssignerAMZN
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-03-16 17:16:32 UTC
Updated2026-05-21 15:58:19 UTC
DescriptionImproper 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.

Risk And Classification

Primary CVSS: v4.0 6.8 MEDIUM from ff89ba41-3aa1-4d27-914a-91399e9639e5

CVSS: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

EPSS: 0.000190000 probability, percentile 0.055920000 (date 2026-05-27)

Problem Types: CWE-424 | CWE-424 CWE-424: Improper Protection of Alternate Path

VersionSourceTypeScoreSeverityVector
4.0ff89ba41-3aa1-4d27-914a-91399e9639e5Secondary6.8MEDIUMCVSS: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/C...
4.0CNACVSS6.8MEDIUMCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
3.1ff89ba41-3aa1-4d27-914a-91399e9639e5Secondary5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
3.1CNACVSS5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

CVSS v4.0 Breakdown

Attack Vector
Local
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
Passive
Confidentiality
High
Integrity
None
Availability
None
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS: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 v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Amazon Aws Api Mcp Server All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA AWS AWS API MCP Server affected 0.2.14 1.3.9 custom Not specified

References

ReferenceSourceLinkTags
pypi.org/project/awslabs.aws-api-mcp-server/1.3.9 ff89ba41-3aa1-4d27-914a-91399e9639e5 pypi.org Third Party Advisory
aws.amazon.com/security/security-bulletins/2026-007-AWS ff89ba41-3aa1-4d27-914a-91399e9639e5 aws.amazon.com Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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