HIGH CVSS 7.5
Published: 2026-03-16

CVE-2026-4269

amazon bedrock_agentcore_starter_toolkit Security Advisory (CVE-2026-4269)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-4269 impacting amazon bedrock_agentcore_starter_toolkit. Evaluated with CVSS Base Score of 7.5 (HIGH).

Original NVD Description

Source: NIST NVD
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 v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
High (AC:H)
Depends on race conditions or environment
Privileges Required
None (PR:N)
Unauthenticated execution
User Interaction
Required (UI:R)
User must click or open resource
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
High (C:H)
Total information disclosure
Integrity
High (I:H)
Total modification of target system
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product amazon / bedrock_agentcore_starter_toolkit
Affected Versions *
Weakness Enumeration CWE-283

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2026-4269 impacting amazon bedrock_agentcore_starter_toolkit.

⚡ Nuclei Detection Template (YAML) cve-2026-4269.yaml
id: cve-2026-4269

info:
  name: amazon bedrock_agentcore_starter_toolkit - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-4269 affecting amazon bedrock_agentcore_starter_toolkit.
    Evaluation: 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...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-4269
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
    cvss-score: 7.5
    cve-id: CVE-2026-4269
    cwe-id: CWE-283
  tags: cve,cve-2026-4269,amazon,bedrock_agentcore_starter,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "bedrock_agentcore_starter_toolkit"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-4269.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-4269
# Target: amazon bedrock_agentcore_starter_toolkit | CVSS: 7.5 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-4269 (amazon bedrock_agentcore_starter_toolkit)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against amazon bedrock_agentcore_starter_toolkit scope (*).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2026-4269.sh
# Recommended Remediation & Patching Commands for CVE-2026-4269
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install bedrock_agentcore_starter 2>/dev/null || \
sudo dnf upgrade bedrock_agentcore_starter 2>/dev/null || \
sudo yum update bedrock_agentcore_starter

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i bedrock_agentcore_starter 2>/dev/null || rpm -qa | grep -i bedrock_agentcore_starter

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

🔗 Verified Technical References

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-4269 in amazon bedrock_agentcore_starter_toolkit?

Review vendor-specific security notices and update amazon bedrock_agentcore_starter_toolkit packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2026-4269?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2026-4269?

CVE-2026-4269 is classified with a CVSS 3.1 Base Score of 7.5 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
7.5
HIGH SEVERITY
CVE ID CVE-2026-4269
Weakness CWE-283
Vendor amazon
Product bedrock_agentcore_starter_toolkit
Published 2026-03-16
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H