High severity · published Mar 16, 2026
CVE-2026-4269
Improper S3 ownership verification in Bedrock AgentCore Starter Toolkit
7.5
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
High
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 17% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
BA
Bedrock AgentCore Starter Toolkit · AWS
0.1.0 before 0.1.13 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-4269
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-4269
Vendor Advisory
https://aws.amazon.com/security/security-bulletins/2026-008-AWS/
Release Notes
https://github.com/aws/bedrock-agentcore-starter-toolkit/releases/tag/v0.1.13
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