CVE-2026-26282: NanaZip Information Disclosure Flaw

CVE-2026-26282 Overview

CVE-2026-26282 is an out-of-bounds heap read vulnerability in NanaZip, an open source file archiver. The vulnerability exists in the .NET Single File bundle header parser due to a missing bounds check. When a user opens a specially crafted file with NanaZip, the application may crash or leak heap data to the user.

Critical Impact

Opening maliciously crafted files can cause application crashes (denial of service) or leak sensitive heap memory contents to attackers.

Affected Products

• NanaZip version 5.0.1252.0 and later
• NanaZip versions prior to 6.0.1630.0
• NanaZip installations processing .NET Single File bundles

Discovery Timeline

• 2026-02-19 - CVE-2026-26282 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2026-26282

Vulnerability Analysis

This vulnerability is classified as CWE-126 (Buffer Over-read), which occurs when a program reads data past the end of the intended buffer. In the context of NanaZip, the .NET Single File bundle header parser fails to properly validate the bounds of input data before performing read operations on the heap.

The attack requires local access and user interaction, as the victim must open a malicious archive file. While the confidentiality impact is limited, the availability impact is significant as the vulnerability can reliably crash the application. The heap data that may be leaked could potentially contain sensitive information depending on what was previously stored in memory.

Root Cause

The root cause of CVE-2026-26282 is a missing bounds check in the .NET Single File bundle header parsing routine. When NanaZip processes the header of a .NET Single File bundle, it fails to validate that the size fields and offset values within the header are within the boundaries of the allocated buffer. This allows crafted input to cause the parser to read beyond the allocated heap memory region.

Attack Vector

The attack vector is local and requires user interaction. An attacker must craft a malicious file that appears to be a valid .NET Single File bundle but contains manipulated header values. The attack scenario involves:

1. The attacker creates a specially crafted file with malformed .NET Single File bundle headers
2. The victim receives the malicious file (via email, download, or other means)
3. The victim opens or extracts the file using NanaZip
4. The vulnerable parser reads heap data beyond allocated boundaries
5. This results in either an application crash or leakage of heap memory contents

The exploitation mechanism takes advantage of the parser trusting size and offset values within the bundle header without validating them against the actual allocated buffer size. A proof-of-concept is available through the GitHub PoC Repository.

Detection Methods for CVE-2026-26282

Indicators of Compromise

• Unexpected NanaZip application crashes when processing archive files
• Memory access violation errors in NanaZip during file extraction operations
• Crash dump files showing out-of-bounds memory access in .NET Single File bundle parsing code

Detection Strategies

• Monitor for repeated NanaZip crashes associated with specific archive files
• Implement endpoint detection rules for memory access violations in NanaZip processes
• Deploy file integrity monitoring to detect suspicious archive files being introduced to systems

Monitoring Recommendations

• Enable application crash reporting and logging for NanaZip installations
• Monitor for abnormal memory access patterns in file archiver processes
• Review system event logs for application exceptions related to NanaZip

How to Mitigate CVE-2026-26282

Immediate Actions Required

• Upgrade NanaZip to version 6.0.1630.0 or later immediately
• Exercise caution when opening archive files from untrusted sources
• Consider temporarily using alternative archive utilities until patching is complete

Patch Information

The vulnerability has been patched in NanaZip version 6.0.1630.0. Organizations should update all NanaZip installations to this version or later. The patch adds proper bounds checking to the .NET Single File bundle header parser to prevent out-of-bounds heap reads. For more details, see the GitHub Security Advisory.

Workarounds

• Avoid opening .NET Single File bundle archives from untrusted sources until patched
• Use alternative archive utilities that are not affected by this vulnerability
• Implement application whitelisting to prevent execution of malicious archive contents
• Deploy endpoint protection solutions to detect and block exploitation attempts