Heap Out-of-Bounds Read in Unshield

Executive Summary

This is a heap out-of-bounds read vulnerability in the unshield library through version 1.6.2. It occurs in the unshield_get_file_table() function where attackers can supply a crafted InstallShield cabinet file with invalid file_table_offset or excessive file counts. This causes the function to read memory beyond allocated heap space, potentially crashing the unshield tool or any application using the library.

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Detection Guidance

To detect this vulnerability, inspect unshield versions on your system. Run 'unshield --version' or check package managers like 'dpkg -l | grep unshield' or 'rpm -qa | grep unshield'. If using a vulnerable version (1.6.2 or earlier), the tool may crash when processing crafted CAB files. Use static analysis tools like AddressSanitizer during compilation to identify heap out-of-bounds reads.

Test with a proof-of-concept CAB file if available. Commands like 'unshield l test.cab' may trigger crashes if the file contains malicious offsets. Monitor system logs for segmentation faults during unshield operations.

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Impact Analysis

This vulnerability can cause denial of service by crashing the unshield tool or any application relying on it when processing a malicious cabinet file. It does not lead to code execution or information disclosure but may disrupt operations dependent on unshield for extracting InstallShield cabinet archives.

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Compliance Impact

This vulnerability does not directly affect compliance with GDPR or HIPAA as it is a denial-of-service issue causing crashes rather than unauthorized data access or disclosure. However, if unshield is used in systems processing sensitive data under these regulations, repeated crashes could disrupt operations, potentially leading to service unavailability or data processing delays.

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Mitigation Strategies

Upgrade unshield to the latest version beyond 1.6.2 if available. If no patch exists, avoid using unshield on untrusted CAB files. Disable or remove unshield from systems where it is not essential. Implement input validation for CAB files processed by your applications.

Monitor for crashes in unshield processes and apply network-level controls to block suspicious CAB file transfers. Consider using alternative tools like i5comp or i6comp if they are patched or trusted.

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