CVE-2025-51602: VLC Media Player DoS Vulnerability

CVE-2025-51602 Overview

CVE-2025-51602 is an out-of-bounds read vulnerability in the mmstu.c component of VideoLAN VLC media player versions prior to 3.0.22. The vulnerability allows an attacker to trigger an out-of-bounds read condition and denial of service through a specially crafted 0x01 response from a malicious MMS (Microsoft Media Server) server. When VLC processes the malformed response, it reads memory beyond the intended buffer boundaries, potentially causing the application to crash.

Critical Impact

A remote attacker operating a malicious MMS server can crash VLC media player on connecting clients, causing denial of service and potentially leaking sensitive memory contents.

Affected Products

• VideoLAN VLC media player versions before 3.0.22
• Systems connecting to MMS streaming servers

Discovery Timeline

• 2026-01-16 - CVE CVE-2025-51602 published to NVD
• 2026-01-16 - Last updated in NVD database

Technical Details for CVE-2025-51602

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), a memory corruption issue that occurs when the software reads data past the end or before the beginning of the intended buffer. In the context of VLC's MMS protocol handler, the mmstu.c file contains parsing logic for responses from MMS streaming servers.

When processing a specific 0x01 response type from an MMS server, the code fails to properly validate the boundaries of the data being read. This allows a malicious server to send a crafted response that causes VLC to read memory beyond the allocated buffer, leading to potential information disclosure and application crashes.

The vulnerability requires network access and the attacker must control or compromise an MMS server that the victim connects to. While user interaction is not explicitly required for the vulnerability itself, the victim must initiate a connection to the malicious server, which adds complexity to the attack scenario.

Root Cause

The root cause lies in insufficient boundary checking in the MMS protocol parsing code within mmstu.c. When the function processes 0x01 response packets from an MMS server, it does not adequately verify that the data lengths and offsets provided in the server response are within valid buffer boundaries. This missing validation allows the server to specify values that cause reads outside the allocated memory region.

Attack Vector

The attack vector is network-based, requiring the attacker to operate a malicious MMS server or perform a man-in-the-middle attack on MMS connections. The attack scenario involves:

1. An attacker sets up a rogue MMS server or compromises an existing one
2. A victim connects to the server using VLC media player (versions prior to 3.0.22)
3. The server sends a malformed 0x01 response with crafted values
4. VLC's MMS handler in mmstu.c processes the response without proper bounds checking
5. An out-of-bounds read occurs, causing denial of service or potential memory disclosure

The vulnerability manifests when VLC's MMS protocol handler parses server responses. For detailed technical analysis, refer to VLC Issue #29146 and the VideoLAN Security Bulletin VLC-3022.

Detection Methods for CVE-2025-51602

Indicators of Compromise

• VLC media player crashes or unexpected terminations when connecting to streaming servers
• Abnormal MMS protocol traffic with malformed 0x01 response packets
• Memory access violation errors in system logs related to VLC processes

Detection Strategies

• Monitor for VLC application crashes with fault addresses in the mmstu.c module or MMS-related libraries
• Implement network monitoring to detect unusual MMS protocol traffic patterns or malformed MMS responses
• Use endpoint detection solutions to identify repeated VLC crashes that may indicate exploitation attempts
• Review application logs for access violations or segmentation faults during media streaming sessions

Monitoring Recommendations

• Enable crash reporting and logging for VLC media player on enterprise endpoints
• Deploy network intrusion detection signatures for malformed MMS protocol traffic
• Monitor for connections to unknown or untrusted MMS streaming servers
• Implement SentinelOne Singularity Platform for real-time detection of memory corruption exploitation attempts

How to Mitigate CVE-2025-51602

Immediate Actions Required

• Update VLC media player to version 3.0.22 or later immediately
• Block or restrict MMS protocol traffic at the network perimeter if not required for business operations
• Avoid connecting to untrusted or unknown MMS streaming servers
• Deploy endpoint protection solutions capable of detecting application exploitation

Patch Information

VideoLAN has addressed this vulnerability in VLC media player version 3.0.22. The fix implements proper boundary validation for MMS server responses in the mmstu.c component. Users and administrators should upgrade to version 3.0.22 or later to remediate this vulnerability.

For official patch information, refer to the VideoLAN Security Bulletin VLC-3022.

Workarounds

• Disable MMS protocol support in VLC if not required (via preferences or command-line options)
• Use alternative streaming protocols such as HTTP or HTTPS where possible
• Implement network-level blocking of MMS traffic to untrusted servers
• Run VLC in a sandboxed environment to limit the impact of potential exploitation

# Block MMS traffic at the firewall (iptables example)
iptables -A OUTPUT -p tcp --dport 1755 -j DROP
iptables -A OUTPUT -p udp --dport 1755 -j DROP