CVE-2020-6109: Zoom Client Path Traversal Vulnerability

CVE-2020-6109 Overview

An exploitable path traversal vulnerability exists in the Zoom client version 4.6.10 that processes messages including animated GIFs. A specially crafted chat message can cause an arbitrary file write, which could potentially be abused to achieve arbitrary code execution. An attacker needs to send a specially crafted message to a target user or a group to exploit this vulnerability.

Critical Impact

This vulnerability allows remote attackers to achieve arbitrary code execution through a specially crafted chat message containing a malicious GIF, requiring no privileges or user interaction beyond being in the same chat.

Affected Products

• Zoom Client version 4.6.10

Discovery Timeline

• 2020-06-08 - CVE-2020-6109 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-6109

Vulnerability Analysis

This path traversal vulnerability (CWE-22) exists in how the Zoom client handles animated GIF messages. When processing GIF files shared through chat, the application fails to properly sanitize file path components, allowing attackers to write files to arbitrary locations on the target system. The vulnerability is particularly concerning because it can be exploited remotely over the network with no authentication required and without any user interaction beyond the victim receiving the malicious message.

The attack surface is significant given Zoom's widespread use in enterprise and personal communications. An attacker positioned in the same meeting, chat room, or direct message conversation can silently exploit this vulnerability to compromise target systems.

Root Cause

The root cause of CVE-2020-6109 lies in improper input validation when processing GIF file paths within chat messages. The Zoom client fails to properly sanitize directory traversal sequences (such as ../) in file paths extracted from GIF-related data. This allows an attacker to escape the intended directory structure and write files to arbitrary locations on the filesystem, bypassing the application's expected file handling boundaries.

Attack Vector

The attack vector leverages the Zoom chat functionality to deliver a maliciously crafted message containing a specially formatted GIF. The attack flow operates as follows:

1. The attacker crafts a chat message containing a GIF with embedded path traversal sequences
2. The message is sent to a target user or group through Zoom's chat feature
3. When the Zoom client processes the message, it fails to sanitize the malicious path components
4. The arbitrary file write occurs without user interaction or authentication requirements
5. The attacker can leverage the file write primitive to achieve code execution by writing to startup locations, overwriting critical files, or placing executable content in predictable locations

For detailed technical analysis, refer to the Talos Intelligence Vulnerability Report.

Detection Methods for CVE-2020-6109

Indicators of Compromise

• Unexpected file creation or modification outside of standard Zoom cache and data directories
• Files written to system startup folders or other sensitive locations by the Zoom process
• Anomalous GIF file processing patterns in Zoom client logs
• Presence of directory traversal sequences (../) in Zoom-related file paths

Detection Strategies

• Monitor the Zoom client process for file write operations outside of expected directories such as %AppData%\Zoom and temporary folders
• Implement file integrity monitoring on critical system directories to detect unauthorized file writes
• Deploy endpoint detection rules that alert on path traversal patterns in file operations initiated by the Zoom process
• Analyze network traffic for unusual GIF payloads or chat message patterns targeting Zoom clients

Monitoring Recommendations

• Enable comprehensive file system auditing for Zoom client processes on endpoints
• Configure SIEM rules to correlate Zoom process activity with unexpected file system modifications
• Implement network-level inspection for Zoom chat traffic containing suspicious GIF attachments
• Review Zoom client logs for error conditions that may indicate exploitation attempts

How to Mitigate CVE-2020-6109

Immediate Actions Required

• Update Zoom client to a version newer than 4.6.10 immediately
• Restrict Zoom usage to trusted participants until patching is complete
• Enable endpoint protection monitoring for Zoom client processes
• Consider temporarily disabling GIF rendering in chat if supported by your Zoom configuration

Patch Information

Organizations should update the Zoom client beyond version 4.6.10 to remediate this vulnerability. Consult the Talos Intelligence Vulnerability Report for additional technical details and verify the latest secure version through official Zoom channels.

Workarounds

• Restrict Zoom chat functionality to internal trusted users only where possible
• Implement network segmentation to limit exposure of vulnerable Zoom clients
• Deploy application control policies to monitor and restrict Zoom process file write operations
• Consider using web-based Zoom interfaces instead of the desktop client until patched versions are deployed

For enterprise deployments, consider implementing the following network restrictions to limit exposure:

# Example firewall rule to log suspicious Zoom traffic (adjust for your environment)
# Monitor for unusual file transfer patterns
iptables -A OUTPUT -p tcp --dport 443 -m owner --uid-owner zoom -j LOG --log-prefix "ZOOM_TRAFFIC: "

# Consider restricting Zoom to specific trusted network segments
# iptables -A INPUT -s <trusted_network> -p tcp --dport 8801 -j ACCEPT
# iptables -A INPUT -p tcp --dport 8801 -j DROP