CVE-2026-4269Network attack vector

Runtime code execution via unverified S3 bucket ownership

Published Mar 16, 2026 · Updated Mar 16, 2026

Code injection in Amazon Web Services Bedrock AgentCore Starter Toolkit before 0.1.13 allows remote attackers to execute code at runtime. CodeBuildService uses predictable S3 bucket names and performs S3 operations without confirming that the bucket belongs to the caller's AWS account, allowing attacker-owned build content to enter the image. Exposure requires an affected toolkit build after September 24, 2025 and user interaction with the build; the resulting code runs in the AgentCore Runtime.

CVSS severity5.8
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Code injection in Amazon Web Services Bedrock AgentCore Starter Toolkit before 0.1.13 allows remote attackers to execute code at runtime. CodeBuildService uses predictable S3 bucket names and performs S3 operations without confirming that the bucket belongs to the caller's AWS account, allowing attacker-owned build content to enter the image. Exposure requires an affected toolkit build after September 24, 2025 and user interaction with the build; the resulting code runs in the AgentCore Runtime.

The record

CVE
CVE-2026-4269
Published
Mar 16, 2026
Updated
Mar 16, 2026
Vendor
Amazon Web Services
Product
Bedrock AgentCore Starter Toolkit
Classifications
CWE-340, CWE-283, T1195.002
Attack vector
network
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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=0.1.0 <0.1.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Amazon Web Services · Bedrock AgentCore Starter Toolkitversion=0.1.0 <0.1.13

Published CVSS scores

5.8Amazon Web ServicesCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H
7.5Amazon Web ServicesCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-340Generation of Predictable Numbers or Identifiers
CWE-283Unverified Ownership
T1195.002Compromise Software Supply Chain

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo