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🛡️ CVE-2026-4269 — bedrock-agentcore-starter-toolkit

🟠 CVSS 7.5 — High ✅ No Known Exploit CWE-283 OSV
7.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Improper S3 ownership verification in Bedrock AgentCore Starter Toolkit

Summary

An issue has been identified in the Bedrock AgentCore Starter Toolkit versions prior to v0.1.13 that may allow a remote actor to inject code during the build process, leading to code execution in the AgentCore Runtime.

Impact

A remote actor could inject code during the build process, leading to code execution in the AgentCore Runtime and a complete loss of confidentiality, integrity, and availability of the affected AgentCore resource.

Impacted versions: All versions of Bedrock AgentCore Starter Toolkit versions before v0.1.13. This issue only affects users of the Bedrock AgentCore Starter Toolkit before version v0.1.13 who build 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 date are not affected.

Patches

This issue has been addressed in version v0.1.13. AWS recommends upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.

Workarounds

N/A

References

If you have any questions or comments about this advisory, contact [AWS/Amazon] Security via our [vulnerability reporting page](https://aws.amazon.com/security/vulnerability-reporting) or directly via email to [[email protected]](mailto:[email protected]). Please do not create a public GitHub issue.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. A user must be tricked into taking some action. Rated impact: confidentiality none, integrity none, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
  • Attack requirements: None — no deployment-specific condition has to hold.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: Passive — a victim action is involved, but not a deliberate one.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: None.

Weakness class

CVE-2026-4269 is classified as CWE-283: Unverified Ownership. The product does not properly verify that a critical resource is owned by the proper entity.

Affected software

CVE-2026-4269 is recorded against 1 package.

  • bedrock-agentcore-starter-toolkit (fixed in 0.1.13)

Timeline and source

Published on 13 July 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

github.com (Web)
nvd.nist.gov (Advisory)
aws.amazon.com (Web)
github.com (Package)
github.com (Web)
pypi.org (Package)
github.com (Advisory)

Same weakness in other software

These advisories are the same class of weakness (CWE-283: Unverified Ownership) in other software:

Details

Severity HIGH
CVSS Score 7.5
CVSS Vector CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H
CWE CWE-283
Public Exploit ✅ No
Source OSV
Published 2026-07-13
Updated 2026-08-20
Modified 2026-07-13
Fix URL N/A

Affected Packages

Software From version Fixed in
bedrock-agentcore-starter-toolkit — 0.1.13

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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