CVE-2024-33894

Executive Summary

CVE-2024-33894 identifies a critical insecure permission vulnerability in Cosy+ devices running specific firmware versions. The flaw allows processes to execute with elevated privileges due to misconfigured permissions, potentially enabling an attacker to gain unauthorized access or escalate privileges on the device. This vulnerability affects firmware versions 21.x below 21.2s10 and 22.x below 22.1s3. No public proof-of-concept or exploit code is currently available, and the CVSS score is listed as 0.0, likely due to incomplete scoring data. The vendor has released patches in the form of firmware updates.

CVSS Breakdown & Threat Level

The CVSS score is reported as 0.0, which is atypical and likely indicates that the scoring vector has not been fully assigned or published by NVD. Without a complete vector, the threat level cannot be precisely determined. However, based on the nature of the vulnerability (insecure permissions leading to elevated privileges), the potential impact could be high, affecting confidentiality, integrity, and availability of the device. The EPSS score of 0.0% suggests low exploitation probability in the wild at this time.

Deep Dive & Mechanics

The vulnerability stems from insecure permission settings on Cosy+ devices. Specifically, several system processes are configured to run with elevated privileges (e.g., root or SYSTEM) without proper access controls. This misconfiguration allows any user or process with local access to potentially exploit these elevated processes, leading to privilege escalation or unauthorized actions. The affected firmware versions are 21.x (below 21.2s10) and 22.x (below 22.1s3). The root cause is likely improper file or process permission assignments during the firmware build process.

Vulnerable vs. Patched Code

No specific code snippets are available for this vulnerability. The patch involves updating the firmware to versions 21.2s10 or 22.1s3, which presumably corrects the permission settings for the affected processes. The vendor has not released detailed changelogs or code diffs publicly.

Exploitation & Lab Setup

Red Team

Since no public exploit code is available, a red team would need to perform manual analysis. The following steps outline a potential approach:

1. Identify Target: Scan for Cosy+ devices on the network using Shodan dorks or network scanning.
2. Access Device: Gain initial access via default credentials or other vulnerabilities.
3. Enumerate Processes: List running processes and identify those with elevated privileges.
4. Exploit Permissions: Attempt to interact with or manipulate the elevated processes to escalate privileges or execute arbitrary commands.

Example enumeration command (once on the device):

ps aux | grep -E "root|SYSTEM"

Blue Team

Blue team defenders should:

1. Monitor for Unauthorized Access: Use network monitoring to detect scans or login attempts targeting Cosy+ devices.
2. Audit Permissions: Regularly review process and file permissions on Cosy+ devices.
3. Apply Patches: Immediately upgrade firmware to patched versions.
4. Restrict Access: Limit network exposure of Cosy+ devices to trusted IPs only.

Indicators of Compromise (IOCs)

• Network: Unusual traffic to/from Cosy+ devices on ports commonly used for management (e.g., SSH, HTTP).
• System: Unexpected processes running with elevated privileges, or modifications to system binaries.
• Logs: Failed login attempts or privilege escalation events in system logs.

Detection Engineering

YARA Rule

rule CVE_2024_33894_Cosy_Insecure_Permissions {
    meta:
        description = "Detects insecure permission patterns in Cosy+ firmware"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-33894"
    strings:
        $s1 = "chmod 777" nocase
        $s2 = "chown root:root" nocase
        $s3 = "SUID" nocase
    condition:
        any of them
}

Sigma Rule

title: CVE-2024-33894 - Cosy+ Insecure Permission Exploitation
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects attempts to exploit insecure permissions on Cosy+ devices
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/chmod'
        CommandLine|contains: '777'
    condition: selection
falsepositives:
    - Legitimate administrative actions
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-33894 - Cosy+ Insecure Permission Exploitation Attempt"; flow:to_server; content:"chmod 777"; nocase; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Upgrade all Cosy+ devices to firmware version 21.2s10 (for 21.x) or 22.1s3 (for 22.x).
2. Access Control: Restrict network access to Cosy+ devices using firewalls or VLANs.
3. Monitoring: Implement logging and monitoring for unusual process behavior.
4. Vendor Contact: If unable to patch, contact Cosy support for interim mitigations.

Valters IT
DevSecOps & Cyber Threat Intelligence