CVE-2024-34596

Executive Summary

CVE-2024-34596 is an improper authentication vulnerability in SmartThings prior to version 1.8.17. The flaw allows remote attackers to bypass the expiration date for members set by the owner, potentially granting unauthorized access to the SmartThings ecosystem beyond the intended time limit. This vulnerability has a CVSS score of 5.9 (Medium) and an EPSS score of 0.0%, indicating low exploitation likelihood at this time. No public proof-of-concept or exploit code is available, and the vendor has not released a patch.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects the SmartThings application, which is a proprietary IoT platform. No open-source package dependencies are involved.

CVSS Breakdown & Threat Level

• CVSS Score: 5.9 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: Low
• Availability Impact: Low

The threat level is considered medium due to the low complexity and no required privileges, but the impact is limited to integrity and availability of member expiration controls.

Deep Dive & Mechanics

The vulnerability lies in the authentication mechanism for member expiration dates in SmartThings. When an owner sets an expiration date for a member, the system should enforce that date and revoke access after it passes. However, due to improper authentication, remote attackers can bypass this expiration check, allowing members to continue accessing the SmartThings ecosystem beyond the intended period.

The root cause is likely a failure to validate the expiration timestamp on the server side, or a client-side check that can be manipulated. The attacker does not need to be authenticated to exploit this, as the bypass occurs during the authentication process itself.

Vulnerable vs. Patched Code

No specific code snippets are available for this vulnerability. However, the vulnerable behavior can be described as:

Vulnerable (pre-1.8.17):

• The application accepts member authentication tokens without verifying the expiration date.
• The expiration date is stored client-side or not enforced server-side.

Patched (1.8.17+):

• The application validates the expiration date on the server side before granting access.
• Member tokens are rejected if the expiration date has passed.

Exploitation & Lab Setup

Red Team

Since no public exploit code is available, a red team would need to reverse-engineer the SmartThings API to identify the authentication bypass. The following steps outline a potential approach:

1. Setup: Obtain a SmartThings hub and create an owner account with a member invitation set to expire.
2. Intercept Traffic: Use a proxy like Burp Suite to capture the authentication request when the member logs in.
3. Analyze Request: Look for parameters related to expiration (e.g., expires_at, valid_until).
4. Modify Request: Change the expiration parameter to a future date or remove it entirely.
5. Replay Request: Send the modified request to see if the server accepts it.
6. Verify: Check if the member can still access the hub after the original expiration date.

Example Burp Suite Interception:

POST /api/v1/authenticate HTTP/1.1
Host: api.smartthings.com
Content-Type: application/json

{
  "token": "member_token_here",
  "expires_at": "2024-01-01T00:00:00Z"
}

Modified Request:

POST /api/v1/authenticate HTTP/1.1
Host: api.smartthings.com
Content-Type: application/json

{
  "token": "member_token_here",
  "expires_at": "2099-01-01T00:00:00Z"
}

Blue Team

To detect exploitation attempts, monitor for:

• Repeated authentication requests with modified expiration parameters.
• Anomalous access patterns from members after their expiration date.
• Logs showing successful authentication for expired members.

Detection Steps:

1. Enable logging on the SmartThings hub or API gateway.
2. Monitor for authentication requests with expires_at values far in the future.
3. Alert on any member access after their scheduled expiration.

Indicators of Compromise (IOCs)

• Network: Unusual authentication requests to SmartThings API with modified expiration timestamps.
• Logs: Authentication success for members whose expiration date has passed.
• Behavior: Members accessing the hub after their intended expiration period.

Detection Engineering

YARA Rule

rule CVE_2024_34596_SmartThings_AuthBypass {
    meta:
        description = "Detects SmartThings authentication bypass attempts"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-34596"
    strings:
        $expires = "expires_at" nocase
        $token = "token" nocase
        $future_date = /20[2-9][0-9]-[0-1][0-9]-[0-3][0-9]T[0-2][0-9]:[0-5][0-9]:[0-5][0-9]Z/  // Matches dates from 2020 onwards
    condition:
        all of them
}

Sigma Rule

title: SmartThings Authentication Bypass Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects attempts to bypass member expiration in SmartThings
author: Valters IT
date: 2024-01-01
references:
    - CVE-2024-34596
logsource:
    category: application
    product: smartthings
detection:
    selection:
        event: "authentication"
        expires_at|re: "20[2-9][0-9]-[0-1][0-9]-[0-3][0-9]T[0-2][0-9]:[0-5][0-9]:[0-5][0-9]Z"
    condition: selection
falsepositives:
    - Legitimate long-term member access
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-34596 SmartThings Authentication Bypass"; flow:to_server; content:"POST"; http_method; content:"/api/v1/authenticate"; http_uri; content:"expires_at"; http_client_body; pcre:"/20[2-9][0-9]-[0-1][0-9]-[0-3][0-9]T[0-2][0-9]:[0-5][0-9]:[0-5][0-9]Z/"; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Upgrade SmartThings to version 1.8.17 or later as soon as a patch is released.
• Workaround: Manually remove members after their expiration date and re-invite them if needed.
• Monitoring: Implement logging and alerting for authentication anomalies.
• Network Segmentation: Isolate SmartThings hubs on a separate VLAN to limit exposure.

Valters IT