Cyber Resilience

CVE-2026-4270

Amazon Aws Api Mcp Server 0.2.14 – 1.3.9

Published
16 March 2026
Modified
21 May 2026
Patch / advisory
View advisory
CVSS Score v4 6.8
Click a component to see what it means
Raw vectorCVSS: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 Score 0.0013 3th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-4270 is a medium-severity Improper Protection of Alternate Path (CWE-424) vulnerability in Amazon Aws Api Mcp Server. Its CVSS base score is 6.8 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

This vulnerability is AI-related — categorised as AI Agent Protocols and Integrations; in the Protocol-Specific Risks risk domain.

The strongest mitigations our analysis identified map to AC-24 (Access Control Decisions) and AC-25 (Reference Monitor) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A01:2025 Broken Access Control

EU & UK References

Vulnerability Data

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…

more

file contents in the MCP client application context. To remediate this issue, users should upgrade to version 1.3.9.

CWE(s)
CWE-424

AI Security AnalysisAI

AI Category
AI Agent Protocols and Integrations
Risk Domain
Protocol-Specific Risks
OWASP Top 10 for LLMs 2025
None mapped
Classification Reason
Matched keywords: mcp

Related Threats

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1083 File and Directory Discovery Discovery
Adversaries may enumerate files and directories or may search in specific locations of a host or network share for certain information within a file system.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-18953Same vendor: Amazon
CVE-2025-46654Shared CWE-424
CVE-2024-12746Same vendor: Amazon
CVE-2023-51651Same vendor: Amazon
CVE-2025-58079Shared CWE-424
CVE-2025-6250Shared CWE-424
CVE-2023-20272Shared CWE-424
CVE-2025-49162Shared CWE-424
CVE-2025-46655Shared CWE-424
CVE-2025-48828Shared CWE-424

Affected Assets

amazon
aws api mcp server
0.2.14 — 1.3.9

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 6 hardening rules · 4 OS baselines
Validate
Prove the fix (OWASP ASVS)

—

Mitigating Controls (NIST 800-53 r5) AI

AC-24 Access Control Decisions good match

Requiring access-control decisions to be applied to each request ensures no alternate path can bypass authorization checks.

AC-25 Reference Monitor good match

A reference monitor that is always invoked by definition covers every possible path, eliminating the root cause of unprotected alternate paths.

AC-3 Access Enforcement good match

Enforcing approved authorizations for every logical access request structurally blocks unprotected alternate paths to restricted resources.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.AA-05 mostly match
prevents

Enforcing and reviewing authorizations across all access paths directly prevents alternate-path bypasses.

PR.IR-01 partial match
prevents

Logical segmentation and unauthorized-access protections reduce the attack surface of unprotected alternate paths.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.2 Privileged access rights mostly match
prevents

Privileged access rights must be enforced on every possible route to privileged functions.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can discover unprotected alternate paths before release.

A.8.3 Information access restriction mostly match
prevents

Information access restriction mechanisms must close all alternate paths to restricted data or functions.

A.5.15 Access control partial match
prevents

Access control policy directly requires protection of all entry points to restricted functionality.

A.5.18 Access rights partial match
prevents

Managing access rights must cover every alternate path that could bypass intended restrictions.

A.8.20 Networks security partial match
mitigates

Network security can limit some alternate paths but is not the primary control for application-level path protection.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 9 (1 rule)
  • V-271452 OL 9 must use a Linux Security Module configured to enforce limits on system services. prevents CWE-424
RHEL 9 (1 rule)
  • V-258078 RHEL 9 must use a Linux Security Module configured to enforce limits on system services. prevents CWE-424
Ubuntu 22.04 (1 rule)
  • V-260529 Ubuntu 22.04 LTS must be configured so that remote X connections are disabled, unless to fulfill documented and validated mission requirements. prevents CWE-424
Ubuntu 24.04 (1 rule)
  • V-270708 Ubuntu 24.04 LTS must be configured so that remote X connections are disabled, unless to fulfill documented and validated mission requirements. prevents CWE-424

References