CVE-2026-4270Disclosure(amazon / aws_api_mcp_server)

LOWCVSS 6.8 · MEDIUM

Signal is active with 1 mentions in latest observed window

Immediate actions

Patch amazon aws_api_mcp_server systems immediately

Recommended action window: Monitor and triage in normal cycle

NVD 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.

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0.5/ 10 priority

Sources & remediation

Vendor / third-party advisories

Weakness type (CWE)

CWE-424

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

AVAILABLE

Momentum

STABLE

Are you affected?

If you run products in this scope, you should treat this CVE as relevant to your environment.

aws_api_mcp_server

Threat summary

Patch or workaround signal is available
4 mentions across 4 observed days
Momentum state: stable

What's happening

Patch or workaround mentioned in 2 signals
Technical details provided in 4 signals
Disclosure: 2 classified signals
General: 1 classified signal
Peaked 3d ago at 1 mentions (2026-03-16); latest day: 1
4 total mentions across 4 days

Affected systems

Vendors

amazon

Products

aws_api_mcp_server

Deep dive

Activity timeline4 mentions / 4d

Signal classification3 categories

Disclosure

250.0%

General

125.0%

Patch

125.0%

Referenced assets4 URLs

By indicator

Classification over time

Date	Total	Labels

2026-03-16	1	Disclosure1
2026-03-21	1	Disclosure1
2026-03-22	1	General1
2026-05-15	1	Patch1

Full discourse4 posts

AWS Security Digest@AwsSecDigest145d
Patch
Local File Inclusion in AWS Remote MCP Server via CLI Shorthand Syntax Coby Abrams Coby discovered an LFI (CVE-2026-4270) in the official AWS Remote MCP Server that completely bypasses FileAccessMode=NO_ACCESS. The AWS CLI’s shorthand for loading local file contents into command parameters was passed through unsanitized by the MCP server — point it at a sensitive file, trigger an error, and the error response leaks the file contents. Reproducible against http://aws-mcp.us-east-1.api.aws; patched in v1.3.9. 🔍 What matters: the vulnerability abuses CLI file-loading shorthand and server-side lack of input sanitization, not a client bug. ⚠️ Impact: secrets or config files can be exfiltrated via error messages even when NO_ACCESS is set. ✅ Fix: update AWS Remote MCP Server (and any forks) to v1.3.9 or later now. This was first mentioned in AWS Security Digest Issue #254: https://awssecuritydigest.com/past-issues/aws-security-digest-254 Read here: https://www.varonis.com/blog/local-file-inclusion-in-aws-remote-mcp-server
Post summary
CVE-2026‑4270 is a local file inclusion flaw in AWS Remote MCP Server exploited through CLI shorthand; the vulnerability is documented, patches to version 1.3.9 are available, and no active exploitation is reported.
12054731
1.7K followersView on X
Dar Fazulyanov@DarFazulyanov201d
Disclosure
MCP is becoming the #1 attack surface for AI agents, and most teams don't even know it exists. AWS just patched CVE-2026-4270 in their own MCP server. File access restrictions could be completely bypassed, exposing arbitrary local files to any connected AI agent.
Post summary
The note reports that AWS has patched CVE‑2026‑4270 on its MCP server, highlighting that the flaw allowed bypassing file‑access controls to read arbitrary local files for connected AI agents.
2003055
293 followersView on X
ナタリー 🌙@natalie_avfieb200d
General
AWSのMCPサーバで任意ファイルアクセスが可能になる脆弱性（CVE-2026-4270）、AIエージェントの攻撃面が具体化してきた。「推論の裏側にある基盤」の信頼性が試されてる。自律させるなら、基盤の堅牢化はMCP Guard的な発想で一段深める必要がありそう。 #CyberSecurity #MCPGuard
Post summary
The post references CVE-2026-4270 as a vulnerability that permits arbitrary file access on AWS MCP servers, highlighting concerns about AI agent security but offering no specific exploitation, patch, or PoC details.
0001095
86 followersView on X
Vulmon Vulnerability Feed@VulmonFeeds205d
Disclosure
CVE-2026-4270 Path Traversal Vulnerability in AWS API MCP Server Versions 0.2.14 to 1.3.8 https://vulmon.com/vulnerabilitydetails?qid=CVE-2026-4270
Post summary
This post announces a path traversal vulnerability (CVE-2026-4270) in AWS API MCP Server versions 0.2.14 to 1.3.8, with no information on PoC, exploit, or patch.
0001069
4.0K followersView on X

CPE platform detail1 entries

Part:

Vendor:

Product:

Version:

Target SW:

Target HW:

1 of 1 entries

Part	Vendor	Product	Version	Target SW	Target HW
App	amazon	aws_api_mcp_server	-	python	-

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What researchers are saying

CVE-2026-4270

Dar Fazulyanov[verified]@DarFazulyanovDisclosure

The note reports that AWS has patched CVE‑2026‑4270 on its MCP server, highlighting that the flaw allowed bypassing file‑access controls to read arbitrary local files for connected AI agents.

AWS Security Digest@AwsSecDigestPatch

CVE-2026‑4270 is a local file inclusion flaw in AWS Remote MCP Server exploited through CLI shorthand; the vulnerability is documented, patches to version 1.3.9 are available, and no active exploitation is reported.

ナタリー 🌙@natalie_avfiebGeneral

The post references CVE-2026-4270 as a vulnerability that permits arbitrary file access on AWS MCP servers, highlighting concerns about AI agent security but offering no specific exploitation, patch, or PoC details.

Vulmon Vulnerability Feed@VulmonFeedsDisclosure

This post announces a path traversal vulnerability (CVE-2026-4270) in AWS API MCP Server versions 0.2.14 to 1.3.8, with no information on PoC, exploit, or patch.