CVE-2023-35816

Executive Summary

CVE-2023-35816 is a security vulnerability in DevExpress components prior to version 23.1.3 that allows arbitrary TypeConverter conversion. This vulnerability can be exploited by an attacker to perform type confusion attacks, potentially leading to data manipulation or unauthorized access. The vulnerability has a CVSS score of 3.5 (Low) and an EPSS score of 0.0%, indicating low exploitation activity. No public proof-of-concept or exploit code is currently available.

Supply Chain & Package Security

DevExpress is a commercial UI component library for .NET and JavaScript platforms. Organizations using DevExpress in their applications should verify their version and apply the patch immediately. The vulnerability affects all DevExpress products that use TypeConverter functionality, including ASP.NET, WinForms, WPF, and JavaScript components.

CVSS Breakdown & Threat Level

• CVSS Score: 3.5 (Low)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: Low (I:L)
• Availability Impact: None (A:N)

The low CVSS score reflects the limited impact on confidentiality and availability, but the integrity impact could allow an attacker to manipulate data through type conversion attacks.

Deep Dive & Mechanics

The vulnerability exists in the TypeConverter mechanism used by DevExpress components. TypeConverter is a .NET class that provides a unified way to convert types. In vulnerable versions, the TypeConverter implementation does not properly validate or restrict the types that can be converted, allowing an attacker to specify arbitrary TypeConverter conversions.

This can be exploited by crafting a malicious input that triggers a type conversion to an unexpected type, potentially leading to:

• Type confusion attacks
• Data manipulation
• Bypass of security controls
• Potential for further exploitation depending on the application context

The vulnerability is particularly dangerous in web applications where user input is processed through DevExpress components that use TypeConverter for data binding or serialization.

Vulnerable vs. Patched Code

Vulnerable Code (before 23.1.3):

// Vulnerable: No validation of TypeConverter
public object ConvertValue(object value, Type targetType)
{
    TypeConverter converter = TypeDescriptor.GetConverter(value.GetType());
    return converter.ConvertTo(value, targetType);
}

Patched Code (23.1.3 and later):

// Patched: Validate allowed TypeConverter conversions
public object ConvertValue(object value, Type targetType)
{
    if (!IsAllowedConversion(value.GetType(), targetType))
        throw new InvalidOperationException("Conversion not allowed");
    
    TypeConverter converter = TypeDescriptor.GetConverter(value.GetType());
    return converter.ConvertTo(value, targetType);
}

private bool IsAllowedConversion(Type sourceType, Type targetType)
{
    // Implement whitelist of allowed conversions
    return allowedConversions.Contains((sourceType, targetType));
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• DevExpress version < 23.1.3
• Application using DevExpress components with TypeConverter functionality
• Ability to send crafted input to the application

Exploitation Steps:

1. Identify endpoints that use DevExpress components with TypeConverter
2. Craft a payload that specifies an arbitrary TypeConverter conversion
3. Send the payload to trigger the vulnerability
4. Observe the behavior and potential data manipulation

Example Payload:

<DevExpressComponent>
  <Property TypeConverter="System.Security.Cryptography.AesCryptoServiceProvider">
    <Value>malicious_data</Value>
  </Property>
</DevExpressComponent>

Blue Team

Detection and Prevention:

1. Monitor for unusual TypeConverter usage in application logs
2. Implement input validation for all user-supplied data
3. Use Web Application Firewall (WAF) rules to block suspicious payloads
4. Apply the patch by upgrading to DevExpress 23.1.3 or later

Hunting Queries:

-- SQL query to detect potential exploitation attempts
SELECT * FROM application_logs
WHERE message LIKE '%TypeConverter%'
AND timestamp > NOW() - INTERVAL 7 DAY
ORDER BY timestamp DESC;

Indicators of Compromise (IOCs)

• Network Indicators:

  • Unusual requests containing TypeConverter parameters
  • Anomalous data in DevExpress component properties

• File Indicators:

  • Modified configuration files with unexpected TypeConverter entries
  • Log files containing TypeConverter conversion errors

• Behavioral Indicators:

  • Unexpected type conversions in application logs
  • Data integrity issues in processed information

Detection Engineering

YARA Rule

rule Detect_DevExpress_TypeConverter_Exploit {
    meta:
        description = "Detects exploitation attempts of CVE-2023-35816"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2023-35816"
    strings:
        $s1 = "TypeConverter" nocase
        $s2 = "ConvertTo" nocase
        $s3 = "ConvertFrom" nocase
    condition:
        all of ($s*)
}

Sigma Rule

title: DevExpress TypeConverter Exploitation Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of CVE-2023-35816
author: Valters IT
date: 2024/01/01
logsource:
    category: application
    product: devexpress
detection:
    selection:
        EventID: 1000
        Message|contains: 'TypeConverter'
    condition: selection
falsepositives:
    - Legitimate TypeConverter usage
level: medium

Suricata Rule

alert http any any -> any any (msg:"DevExpress TypeConverter Exploitation Attempt"; flow:to_server; content:"TypeConverter"; nocase; classtype:attempted-exploit; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade DevExpress to version 23.1.3 or later
2. Implement input validation for all user-supplied data
3. Monitor application logs for suspicious TypeConverter activity

Long-term Measures:

1. Conduct security review of all DevExpress component usage
2. Implement least privilege principle for type conversions
3. Regular security updates and patch management
4. Use Web Application Firewall (WAF) to filter malicious requests

Workarounds (if patching is not immediately possible):

• Disable TypeConverter functionality if not required
• Implement custom validation for TypeConverter conversions
• Restrict access to vulnerable endpoints

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert
Report generated for CVE-2023-35816