NanaZip .NET Single-File Bundle Allocation Failure

Executive Summary

CVE-2026-55780 is a vulnerability in NanaZip's .NET single-file bundle handler where the extraction buffer size is determined by the bundle entry's Size field without proper validation against the actual file size. This Size field is only checked to be non-negative but not verified for correctness. An attacker can craft a malicious bundle with an entry size set near the maximum integer value, causing the program to attempt an unbounded memory allocation during extraction.

This leads to exceptions such as std::bad_alloc or std::length_error being thrown and escaping across the COM boundary, which can crash the process. The vulnerability arises from improper input validation and exception handling in the extraction logic.

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Impact Analysis

The primary impact of this vulnerability is a denial of service caused by uncontrolled resource consumption and uncaught exceptions during the extraction process.

• An attacker can cause the application to crash by triggering large memory allocations that fail.
• This crash occurs due to exceptions escaping the COM boundary, leading to undefined behavior and process termination.

The attack complexity is low, requiring only low privileges and user interaction, making it relatively easy to exploit.

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Detection Guidance

This vulnerability is related to the NanaZip .NET single-file bundle handler and involves improper validation of the extraction buffer size, which can cause process crashes due to memory allocation errors.

Detection on a network or system would involve monitoring for crashes or abnormal termination of the NanaZip process, especially when extracting .NET single-file bundles.

Since the issue is triggered by crafted bundles with manipulated Size fields, one way to detect potential exploitation attempts is to monitor NanaZip extraction logs or system event logs for exceptions such as std::bad_alloc or std::length_error.

No specific detection commands or network signatures are provided in the available resources.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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Mitigation Strategies

The primary mitigation step is to update NanaZip to version 6.5.1749.0 or later, where this vulnerability has been fixed.

This update includes validation of the Offset and Size fields against the actual bundle size, improved error handling to prevent exceptions from escaping the COM boundary, and a fixed-size extraction buffer to avoid excessive memory allocation.

Until the update can be applied, avoid extracting untrusted or suspicious .NET single-file bundles with NanaZip to reduce the risk of triggering the vulnerability.

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