CVE-2025-67432: MBS DynaPDF Plugin DoS Vulnerability

CVE-2025-67432 Overview

A stack overflow vulnerability exists in the ZBarcode_Encode function of Monkeybread Software MBS DynaPDF Plugin version 21.3.1.1. This vulnerability allows remote attackers to cause a Denial of Service (DoS) condition by sending specially crafted input to the affected function. The vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), indicating that the function fails to properly validate input boundaries before writing data to the stack.

Critical Impact

Remote attackers can exploit this stack overflow vulnerability to crash applications using the MBS DynaPDF Plugin, causing service disruption without requiring authentication or user interaction.

Affected Products

• Monkeybread Software MBS DynaPDF Plugin v21.3.1.1
• Applications utilizing the ZBarcode_Encode function for barcode generation

Discovery Timeline

• 2026-02-12 - CVE-2025-67432 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2025-67432

Vulnerability Analysis

This vulnerability is a stack-based buffer overflow (CWE-121) in the barcode encoding functionality of the MBS DynaPDF Plugin. The ZBarcode_Encode function processes user-supplied input for barcode generation but fails to properly validate the size of incoming data before copying it to a fixed-size stack buffer.

When an attacker provides maliciously crafted input that exceeds the expected buffer size, the function writes beyond the allocated stack memory, corrupting adjacent stack frames. This leads to application instability and ultimately a crash, resulting in denial of service.

The vulnerability can be triggered remotely over a network connection without requiring authentication or user interaction, making it particularly dangerous for applications that expose barcode generation functionality to untrusted users.

Root Cause

The root cause of this vulnerability is insufficient input validation in the ZBarcode_Encode function. The function allocates a fixed-size buffer on the stack to hold barcode data but does not verify that the input data length falls within acceptable bounds before performing memory copy operations. This classic boundary validation oversight allows attackers to overflow the stack buffer with oversized input.

Attack Vector

The attack can be conducted remotely over the network. An attacker crafts malicious input data that exceeds the expected buffer size and sends it to an application utilizing the vulnerable ZBarcode_Encode function. The attack requires no authentication and no user interaction, making exploitation straightforward for applications that expose this functionality.

The attack flow involves:

1. Identifying an application using MBS DynaPDF Plugin v21.3.1.1
2. Sending specially crafted oversized input to the barcode encoding function
3. The malformed input triggers a stack overflow in ZBarcode_Encode
4. Application crashes, causing denial of service

Technical details and proof-of-concept information are available in the GitHub PoC Repository.

Detection Methods for CVE-2025-67432

Indicators of Compromise

• Unexpected application crashes in processes using the MBS DynaPDF Plugin
• Stack corruption error messages in application or system logs
• Abnormal memory access violations related to barcode generation functions
• Repeated crash patterns following receipt of external input

Detection Strategies

• Monitor for repeated application crashes or restarts of services using MBS DynaPDF Plugin
• Implement input validation logging to detect oversized barcode encoding requests
• Deploy application-level crash monitoring to detect stack overflow signatures
• Use memory protection tools to identify stack boundary violations

Monitoring Recommendations

• Configure application performance monitoring to alert on sudden service terminations
• Enable detailed error logging for the barcode generation subsystem
• Monitor network traffic for unusually large payloads directed at barcode encoding endpoints
• Implement rate limiting on barcode generation requests to mitigate DoS impact

How to Mitigate CVE-2025-67432

Immediate Actions Required

• Identify all applications using Monkeybread Software MBS DynaPDF Plugin v21.3.1.1
• Implement input size validation before calling the ZBarcode_Encode function
• Restrict network access to barcode generation functionality where possible
• Monitor affected systems for signs of exploitation attempts

Patch Information

No official vendor patch information is currently available in the NVD database. Organizations should monitor Monkeybread Software's official channels for security updates. In the interim, implementing the workarounds below is strongly recommended to reduce exposure to this vulnerability.

Workarounds

• Implement strict input length validation before passing data to ZBarcode_Encode
• Use application firewalls or web application firewalls to filter oversized requests
• Isolate applications using the vulnerable plugin in sandboxed environments
• Consider temporarily disabling barcode generation features in critical production systems until a patch is available

# Example input validation configuration (application-specific implementation required)
# Set maximum input length for barcode encoding requests
MAX_BARCODE_INPUT_LENGTH=4096

# Validate input before processing
if [ ${#input} -gt $MAX_BARCODE_INPUT_LENGTH ]; then
    echo "Error: Input exceeds maximum allowed length"
    exit 1
fi