CVE-2024-20290: Cisco Secure Endpoint DoS Vulnerability

CVE-2024-20290 Overview

A vulnerability in the OLE2 file format parser of ClamAV could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to an incorrect check for end-of-string values during scanning, which may result in a heap buffer over-read. An attacker could exploit this vulnerability by submitting a crafted file containing OLE2 content to be scanned by ClamAV on an affected device.

Critical Impact

A successful exploit could allow the attacker to cause the ClamAV scanning process to terminate, resulting in a DoS condition on the affected software and consuming available system resources. This could leave endpoints temporarily unprotected against malware threats.

Affected Products

• Cisco Secure Endpoint (Windows)
• Cisco Secure Endpoint Private Cloud
• Fedora 38 and Fedora 39

Discovery Timeline

• February 7, 2024 - CVE-2024-20290 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-20290

Vulnerability Analysis

This vulnerability exists within the OLE2 file format parser component of ClamAV. OLE2 (Object Linking and Embedding 2) is a file format commonly used in Microsoft Office documents and other compound document structures. The vulnerability stems from improper bounds checking during the parsing of OLE2 content.

When ClamAV processes a file containing OLE2 structures, the parser fails to correctly validate end-of-string values. This leads to a heap buffer over-read condition (CWE-125, CWE-126), where the parser reads memory beyond the allocated buffer boundaries. While this vulnerability primarily results in a denial of service rather than code execution, it can cause the ClamAV scanning process to crash, leaving systems temporarily vulnerable.

Root Cause

The root cause is an incorrect check for end-of-string values during the OLE2 file scanning process. The parser does not properly validate string boundaries before reading, allowing reads beyond allocated heap memory. This is classified as both CWE-126 (Buffer Over-read) and CWE-125 (Out-of-bounds Read).

Attack Vector

The attack can be executed remotely over the network without requiring authentication or user interaction. An attacker can exploit this vulnerability by:

1. Crafting a malicious file containing specially formatted OLE2 content
2. Submitting the file to a system where ClamAV is configured to scan incoming files
3. When ClamAV attempts to parse the OLE2 structures, the malformed content triggers the heap buffer over-read
4. The ClamAV scanning process terminates unexpectedly, causing a denial of service

Common attack vectors include email attachments, file uploads to web applications, or any system where files are automatically scanned by ClamAV.

The vulnerability mechanism involves malformed OLE2 structures that exploit the parser's incomplete string boundary validation. When the parser encounters these crafted structures, it attempts to read beyond the allocated buffer, causing a crash. For detailed technical information, see the Cisco Security Advisory.

Detection Methods for CVE-2024-20290

Indicators of Compromise

• Unexpected ClamAV process crashes or restarts
• clamd service repeatedly terminating without explanation
• Presence of files with unusual or malformed OLE2 structures in quarantine or scan queues
• System logs showing memory access violations or segmentation faults related to ClamAV processes

Detection Strategies

• Monitor ClamAV process stability and log files for repeated crash events
• Implement file integrity monitoring to detect unusual OLE2 document structures
• Configure alerting on ClamAV service disruptions using system monitoring tools
• Review system crash dumps for heap buffer over-read patterns in ClamAV components

Monitoring Recommendations

• Enable detailed logging for ClamAV scanning operations
• Set up automated alerts for ClamAV service failures or unexpected restarts
• Monitor resource utilization patterns that may indicate exploitation attempts
• Implement centralized log aggregation for security event correlation

How to Mitigate CVE-2024-20290

Immediate Actions Required

• Update ClamAV to the latest patched version immediately
• Review and apply updates for Cisco Secure Endpoint and Cisco Secure Endpoint Private Cloud
• Fedora users should apply the latest package updates for ClamAV
• Temporarily disable OLE2 scanning if patches cannot be immediately applied (reduces security coverage)

Patch Information

Cisco has released security patches to address this vulnerability. Organizations should consult the Cisco Security Advisory for specific version information and download links. Fedora users can obtain patched packages through the standard package management system as detailed in the Fedora Package Announcements.

Workarounds

• Configure ClamAV to skip OLE2 file scanning temporarily (reduces protection capabilities)
• Implement network-level filtering to quarantine suspicious OLE2 files before they reach endpoints
• Use additional backup antivirus solutions until patches are applied
• Enable rate limiting on file scanning services to mitigate resource exhaustion

# Temporary workaround: Disable OLE2 scanning in clamd.conf
# WARNING: This reduces malware detection capabilities
echo "ScanOLE2 no" >> /etc/clamav/clamd.conf
systemctl restart clamav-daemon