CVE-2026-4269 Improper S3 ownership verification in Bedrock AgentCore Starter Toolkit
Remote attackers can inject code during the build process of the Bedrock AgentCore Starter Toolkit, leading to code execution in the runtime.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-4269?
CVE-2026-4269 is a medium-severity vulnerability in AWS Bedrock AgentCore Starter Toolkit, published on 16 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
A 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.
Which versions are affected by CVE-2026-4269?
3 open source packages ship an affected version, including bedrock-agentcore-starter-toolkit. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
bedrock-agentcore-starter-toolkit PyPI | All versions | 0.1.13 |
bedrock-agentcore-starter-toolkit PyPI | All versions | 0.1.13 |
bedrock-agentcore-starter-toolkit PyPI | All versions | 0.1.13 |
Products include Amazon Bedrock Agentcore Starter Toolkit.
How do I fix CVE-2026-4269?
Upgrade bedrock-agentcore-starter-toolkit to 0.1.13 or later.
Is CVE-2026-4269 being exploited?
There is no known exploitation of CVE-2026-4269 in the wild and no public exploit code.
Sources
Also known as GHSA-xfhr-q72q-jcrj, PYSEC-2026-2396.