CVE-2019-25566: TransMac 12.3 Buffer Overflow Vulnerability

CVE-2019-25566 Overview

CVE-2019-25566 is a buffer overflow vulnerability in TransMac 12.3, a Windows application used for reading and writing Mac-formatted disk images. The vulnerability exists in the volume name field during disk image creation, allowing local attackers to crash the application by supplying an excessively long string. When a user inputs or pastes more than the expected character limit (approximately 1000 characters) into the volume name field, the application fails to properly validate input boundaries, resulting in a buffer overflow condition that causes an application crash.

Critical Impact

Local attackers can cause denial of service by crashing TransMac through maliciously crafted volume name input, disrupting disk image creation workflows and potentially causing data loss for unsaved work.

Affected Products

• TransMac 12.3

Discovery Timeline

• 2026-03-21 - CVE CVE-2019-25566 published to NVD
• 2026-03-23 - Last updated in NVD database

Technical Details for CVE-2019-25566

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-bounds Write), indicating that the application writes data past the allocated buffer boundary when processing the volume name field. The attack requires local access and no special privileges to execute. When exploited, the vulnerability causes a complete application crash, resulting in high availability impact while confidentiality and integrity remain unaffected.

The exploitation is straightforward: an attacker creates a text file containing approximately 1000 repeated characters, then copies and pastes this content into the volume name field during disk image creation. The application does not perform adequate bounds checking on user input, leading to the buffer overflow condition.

Root Cause

The root cause of this vulnerability is improper input validation in the volume name field handler within TransMac 12.3. The application allocates a fixed-size buffer for storing the volume name string but fails to validate the length of user-supplied input before copying it into this buffer. This allows an attacker to supply a string that exceeds the buffer capacity, causing memory corruption and ultimately an application crash.

Attack Vector

The attack vector is local, requiring an attacker to have access to a system where TransMac is installed. The exploitation process involves:

1. Creating a malicious file containing an excessively long string (approximately 1000+ characters)
2. Opening TransMac and initiating the disk image creation workflow
3. Pasting the oversized string into the volume name field
4. Triggering the buffer overflow when the application attempts to process the malformed input

The vulnerability does not require any special privileges or user interaction beyond normal application usage. Technical details and proof-of-concept information are available through the Exploit-DB #46470 entry.

Detection Methods for CVE-2019-25566

Indicators of Compromise

• TransMac application crashes with memory access violation errors
• Windows Event Viewer entries showing application faults for tmac.exe or related TransMac processes
• Presence of text files containing unusually long strings (1000+ characters) in temporary directories

Detection Strategies

• Monitor for repeated TransMac application crashes that may indicate exploitation attempts
• Implement application-level logging to track abnormal input patterns in disk image creation workflows
• Use endpoint detection and response (EDR) tools to identify buffer overflow exploitation patterns in process memory

Monitoring Recommendations

• Configure Windows Error Reporting to alert on TransMac crash events
• Review crash dump files for evidence of memory corruption attacks
• Monitor system stability logs for patterns of application instability that may indicate active exploitation

How to Mitigate CVE-2019-25566

Immediate Actions Required

• Upgrade TransMac to a version newer than 12.3 if available from Acute Systems
• Restrict local access to systems running vulnerable TransMac installations
• Educate users about the risk of copying untrusted content into application input fields

Patch Information

Users should visit the Acute Systems Homepage to check for updated versions of TransMac that address this vulnerability. The latest installer can be obtained from the Acute Systems Installer page. Additional advisory information is available through the VulnCheck Advisory on TransMac.

Workarounds

• Avoid copying and pasting volume names from untrusted sources when creating disk images
• Limit volume name input to reasonable lengths (under 100 characters) manually
• Consider using alternative disk image creation tools until a patched version is available
• Implement application sandboxing to limit the impact of potential crashes

# Restrict TransMac execution to trusted users only (Windows)
icacls "C:\Program Files\TransMac\tmac.exe" /inheritance:r /grant:r Administrators:RX