CVE-2023-47360: VLC Media Player Integer Underflow Flaw

CVE-2023-47360 Overview

CVE-2023-47360 is an Integer Underflow vulnerability affecting Videolan VLC Media Player prior to version 3.0.20. The vulnerability exists in the MMS (Microsoft Media Server) protocol handling code, where an integer underflow leads to an incorrect packet length calculation. This flaw can be exploited by a remote attacker to cause denial of service conditions when a user opens a specially crafted media stream.

Critical Impact

Remote attackers can exploit this integer underflow vulnerability to crash VLC Media Player, resulting in denial of service when users access malicious MMS streams.

Affected Products

• Videolan VLC Media Player versions prior to 3.0.20
• All platforms running vulnerable VLC versions (Windows, macOS, Linux)
• Systems configured to handle MMS protocol streams

Discovery Timeline

• 2023-11-07 - CVE-2023-47360 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-47360

Vulnerability Analysis

This vulnerability is classified as CWE-191 (Integer Underflow). The flaw occurs in the MMS protocol handler within VLC Media Player when processing packet length values. When an arithmetic operation results in a value below the minimum representable integer, an underflow condition occurs, causing the application to calculate an incorrect packet length.

The vulnerability is network-exploitable and requires no authentication or user interaction beyond opening a malicious stream. An attacker can host a specially crafted MMS stream that triggers the underflow condition when parsed by VLC, leading to unexpected application behavior and crashes.

The impact is primarily availability-related, as the vulnerability enables denial of service attacks. While the vulnerability does not directly compromise data confidentiality or integrity, repeated exploitation can disrupt media playback services and user productivity.

Root Cause

The root cause lies in insufficient validation of packet length values in the MMS protocol implementation. When processing MMS streams, VLC performs arithmetic operations on length fields without proper bounds checking. A maliciously crafted packet can supply values that cause the length calculation to underflow, resulting in a negative or unexpectedly large value that corrupts subsequent memory operations.

The integer underflow occurs because the code assumes packet length values will always be within expected bounds, failing to account for edge cases where subtraction operations produce results below zero.

Attack Vector

The attack vector is network-based. An attacker can exploit this vulnerability by:

1. Setting up a malicious MMS server hosting crafted media content
2. Tricking a victim into opening the malicious MMS URL in VLC Media Player
3. The crafted packet triggers the integer underflow during protocol parsing
4. VLC crashes due to the incorrect packet length calculation

The vulnerability can be triggered through social engineering (sending malicious links) or by compromising legitimate streaming servers to inject malicious packets into MMS streams.

For detailed technical analysis of this vulnerability, refer to the 0xAriana blog post which provides in-depth coverage of the MMS protocol handling flaw.

Detection Methods for CVE-2023-47360

Indicators of Compromise

• Unexpected VLC Media Player crashes when accessing MMS protocol streams
• Application crash logs showing memory access violations during MMS parsing
• Network traffic containing malformed MMS protocol packets with unusual length fields
• Repeated crash patterns correlated with specific MMS stream URLs

Detection Strategies

• Monitor for VLC process crashes and analyze crash dumps for MMS-related stack traces
• Implement network intrusion detection rules to identify malformed MMS protocol packets
• Deploy application-level monitoring to detect repeated crashes in VLC Media Player
• Use endpoint detection to correlate crash events with network activity to MMS endpoints

Monitoring Recommendations

• Enable crash reporting and logging for VLC Media Player installations across the organization
• Monitor network traffic for MMS protocol connections to unknown or suspicious servers
• Implement file integrity monitoring on VLC installation directories to verify version compliance
• Track software inventory to identify systems running vulnerable VLC versions

How to Mitigate CVE-2023-47360

Immediate Actions Required

• Upgrade VLC Media Player to version 3.0.20 or later on all affected systems
• Block or restrict access to untrusted MMS streaming sources at the network perimeter
• Educate users about the risks of opening media streams from untrusted sources
• Consider temporarily disabling MMS protocol support if not required for business operations

Patch Information

Videolan has addressed this vulnerability in VLC Media Player version 3.0.20. Organizations should prioritize updating to this version or later to remediate the integer underflow vulnerability. The fix implements proper bounds checking on packet length calculations in the MMS protocol handler.

For additional information, refer to the Debian LTS Announcement which provides distribution-specific patching guidance.

Workarounds

• Avoid opening MMS streams from untrusted or unknown sources until patching is complete
• Use alternative media players that are not affected by this vulnerability as a temporary measure
• Implement network-level filtering to block MMS protocol traffic from external sources
• Configure firewall rules to restrict outbound MMS connections to approved streaming servers only

# Verify VLC version on Linux systems
vlc --version | grep "VLC version"
# Expected output should show version 3.0.20 or higher

# Check for vulnerable versions in package management (Debian/Ubuntu)
apt list --installed | grep vlc
# Update to patched version if necessary
sudo apt update && sudo apt upgrade vlc