Bedrock Agentcore Starter ToolkitApplication · Amazon
CVE-2026-4269
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA missing S3 ownership verification in the Bedrock AgentCore Starter Toolkit before version v0.1.13 may allow a remote actor to inject code during the build process, leading to code execution in the AgentCore Runtime. This issue only affects users of the Bedrock AgentCore Starter Toolkit before version v0.1.13 who build or have built the Toolkit after September 24, 2025. Any users on a version >=v0.1.13, and any users on previous versions who built the toolkit before September 24, 2025 are not affected. To remediate this issue, customers should upgrade to version v0.1.13.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceMissing S3 ownership verification in Bedrock AgentCore Starter Toolkit allows remote attackers to inject malicious code during the build process, resulting in arbitrary code execution in the AgentCore Runtime.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Bedrock Agentcore Starter ToolkitApplication
< 0.1.13CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify the installed version of Bedrock AgentCore Starter ToolkitCheck the package.json, version file, or any version manifest included in the toolkit installation. Run 'npm list @aws.amazon.com/bedrock-agentcore-starter-toolkit' or equivalent package manager command if using Node-based tooling, or inspect the toolkit's version metadata file.Affected if The installed version is lower than 0.1.13 (e.g., 0.1.12, 0.1.10, etc.)
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Locate S3-related build configuration filesSearch the toolkit directory for configuration files that handle S3 bucket interactions during the build process, such as scripts, YAML, JSON, or shell scripts that configure or reference S3 operations.Affected if S3 configuration files exist but do not contain any bucket ownership validation or ownership confirmation logic (e.g., no checks for s3:BucketOwnerFullControl or equivalent ACL/ownership verification)
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Inspect build scripts for S3 ownership verificationExamine any build scripts (e.g., build.sh, deploy.py, cdk.json, or similar) that handle pulling artifacts from or pushing to S3 during the toolkit build process.Affected if The build scripts interact with S3 buckets but lack code that validates bucket ownership or verifies that the bucket belongs to the expected account before using its contents
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Check for environment or config files specifying trusted S3 bucketsLook for environment configuration files, .env files, or infrastructure-as-code templates (CloudFormation, Terraform, CDK) that define which S3 buckets the toolkit is permitted to use.Affected if No explicit bucket ownership or account validation is configured, and the toolkit may accept artifacts from any S3 bucket without verification
You are affected if the toolkit version is below 0.1.13 AND the build process connects to S3 without verifying that the bucket is owned by your own account or a trusted entity.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped0.1.13
Upgrade to version v0.1.13 or later. Users who built the toolkit after September 24, 2025 on versions prior to v0.1.13 are affected and should rebuild with the patched version.
v0.1.13
- Obtain version v0.1.13 of the Bedrock AgentCore Starter Toolkit
- Update your local copy to version v0.1.13
- Rebuild the toolkit to apply the fix
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Bedrock Agentcore Starter Toolkit
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,512.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-4269 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-4269 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data