CVE-2026-4270

Local file disclosure via alternate-path bypass

Published Mar 16, 2026 · Updated Mar 16, 2026

Alternate-path protection failure in AWS API MCP Server 0.2.14 through 1.3.8 allows attackers to read arbitrary local files. AWS has not disclosed which alternate path or code locus bypasses the no-access and workdir file-access checks. Exploitation requires an attacker-influenced request and passive participation by a user or MCP client; disclosure is limited to files readable by the server process.

CVSS severity6.8
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Alternate-path protection failure in AWS API MCP Server 0.2.14 through 1.3.8 allows attackers to read arbitrary local files. AWS has not disclosed which alternate path or code locus bypasses the no-access and workdir file-access checks. Exploitation requires an attacker-influenced request and passive participation by a user or MCP client; disclosure is limited to files readable by the server process.

The record

CVE
CVE-2026-4270
Published
Mar 16, 2026
Updated
Mar 16, 2026
Vendor
Amazon Web Services
Product
AWS API MCP Server
Classifications
CWE-424, T1005
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.2.14 <1.3.9

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Amazon Web Services · AWS API MCP Serverversion=0.2.14 <1.3.9

Published CVSS scores

6.8Amazon Web ServicesCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
5.5GitHub Advisory DatabaseCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-424Improper Protection of Alternate Path
T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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