CVE-2024-5675: Summar Mentor RCE Vulnerability

CVE-2024-5675 Overview

An untrusted data deserialization vulnerability has been discovered in Mentor - Employee Portal, a human resources management application developed by Summar. This critical security flaw affects version 3.83.35 and allows attackers to execute arbitrary code by injecting malicious payloads into the "ViewState" field. The vulnerability stems from improper handling of serialized data, enabling remote attackers to compromise affected systems without authentication.

Critical Impact

This vulnerability enables remote code execution through malicious ViewState deserialization, potentially allowing complete system compromise without requiring authentication.

Affected Products

• Summar Mentor Employee Portal version 3.83.35
• Applications utilizing ASP.NET ViewState without proper validation
• Web-accessible Mentor installations exposed to network access

Discovery Timeline

• 2024-06-06 - CVE-2024-5675 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-5675

Vulnerability Analysis

This vulnerability is classified as an Insecure Deserialization flaw (CWE-502), which occurs when an application deserializes untrusted data without adequate verification. In the context of Mentor Employee Portal, the application fails to properly validate serialized objects received through the ViewState parameter before deserializing them.

ViewState is a mechanism used in ASP.NET web applications to persist page and control values between postbacks. When improperly secured, attackers can craft malicious serialized objects that, upon deserialization, execute arbitrary code on the server. The attack can be conducted remotely over the network and requires no privileges or user interaction, making it highly exploitable.

Root Cause

The root cause of CVE-2024-5675 lies in the application's failure to implement proper validation and integrity checks on ViewState data before deserialization. Without Message Authentication Code (MAC) validation enabled or properly configured, attackers can tamper with the ViewState parameter to include malicious serialized objects. When the server processes this data, the deserialization routine instantiates attacker-controlled objects, leading to arbitrary code execution.

Attack Vector

The attack is conducted remotely over the network by manipulating HTTP requests to the vulnerable Mentor Employee Portal application. An attacker can intercept or craft POST requests containing a malicious ViewState payload. The attack workflow typically involves:

1. Identifying a vulnerable Mentor Employee Portal instance exposed to the network
2. Generating a malicious serialized payload using tools designed for .NET deserialization attacks
3. Encoding the payload appropriately for ViewState transmission
4. Submitting the crafted request to the target application
5. Upon deserialization, the malicious payload executes arbitrary code with the privileges of the web application process

The vulnerability requires no authentication and no user interaction, meaning any network-accessible instance is potentially at risk from automated exploitation.

Detection Methods for CVE-2024-5675

Indicators of Compromise

• Unusual or malformed ViewState parameters in HTTP POST requests to Mentor Employee Portal
• Unexpected process spawning from the web application worker process (e.g., w3wp.exe spawning command shells)
• Anomalous outbound network connections from the web server
• Evidence of encoded serialization gadget chains in web server logs

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to inspect and flag suspicious ViewState payloads containing known deserialization gadgets
• Monitor web server access logs for requests with abnormally large ViewState parameters
• Implement endpoint detection and response (EDR) solutions to identify malicious process execution chains
• Utilize intrusion detection systems (IDS) to alert on known .NET deserialization attack patterns

Monitoring Recommendations

• Enable detailed logging for the Mentor Employee Portal application, particularly for deserialization events
• Configure SIEM alerts for any child processes spawned by the web server application pool
• Monitor for file system modifications in web application directories that could indicate post-exploitation activity
• Track network traffic for command and control (C2) communication patterns originating from web servers

How to Mitigate CVE-2024-5675

Immediate Actions Required

• Restrict network access to Mentor Employee Portal installations to trusted networks only until patched
• Implement WAF rules to block requests with potentially malicious ViewState content
• Enable ViewState MAC validation if not already configured in the ASP.NET application
• Review web server logs for any indicators of exploitation attempts

Patch Information

Administrators should contact Summar directly to obtain information about security patches or updated versions that address this vulnerability. Review the INCIBE security advisory for additional guidance and updates regarding remediation options.

Workarounds

• Place affected Mentor Employee Portal instances behind a VPN or access control mechanism to limit exposure
• Configure the ASP.NET application to enforce ViewState MAC validation by ensuring enableViewStateMac="true" in web.config
• Implement network segmentation to isolate web-facing applications from critical internal systems
• Deploy application-layer filtering to block known deserialization gadget patterns in incoming requests

# ASP.NET web.config mitigation example
# Ensure ViewState MAC validation is enabled:
# <pages enableViewStateMac="true" viewStateEncryptionMode="Always" />

# Additionally, verify machine key is properly configured
# and not using default or weak values