CVE-2026-27711: NanaZip Buffer Overflow Vulnerability

CVE-2026-27711 Overview

CVE-2026-27711 is an Out-of-Bounds Read vulnerability affecting NanaZip, an open source file archiver. A memory corruption vulnerability exists in NanaZip's UFS parser that allows a specially crafted .ufs, .ufs2, or .img file to trigger out-of-bounds memory access during archive open or listing operations. This vulnerability is reachable through the normal user file-open workflow and can result in process crashes, application hangs, and potentially exploitable heap corruption.

Critical Impact

Opening a maliciously crafted archive file can cause denial of service through application crashes or hangs, with potential for heap corruption that may lead to further exploitation.

Affected Products

• NanaZip versions 5.0.1252.0 through versions prior to 6.0.1638.0
• NanaZip versions 5.0.1252.0 through versions prior to 6.5.1638.0

Discovery Timeline

• 2026-02-26 - CVE CVE-2026-27711 published to NVD
• 2026-02-26 - Last updated in NVD database

Technical Details for CVE-2026-27711

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), a memory corruption flaw residing in NanaZip's UFS (Unix File System) parser component. The UFS file system format is commonly used in BSD-derived operating systems, and NanaZip provides functionality to open and list contents of UFS image files.

When processing malformed UFS, UFS2, or IMG archive files, the parser fails to properly validate boundary conditions before accessing memory. This allows an attacker to craft a malicious archive file that, when opened by an unsuspecting user, causes the application to read memory beyond the intended buffer boundaries.

The vulnerability requires local access and user interaction—specifically, a user must open the malicious file through NanaZip's normal file-open interface. While the primary impact is denial of service through crashes or hangs, the heap corruption aspect introduces the possibility of more severe exploitation scenarios depending on memory layout and exploitation techniques.

Root Cause

The root cause of this vulnerability lies in insufficient boundary validation within the UFS parser code. When parsing metadata structures within UFS/UFS2/IMG files, the parser does not adequately verify that offset and size values read from the file remain within valid memory bounds. This allows malformed files with manipulated offset values to cause the parser to access memory outside allocated buffers, resulting in out-of-bounds read operations that corrupt heap memory state.

Attack Vector

This vulnerability requires local access and user interaction to exploit. The attack vector involves:

1. An attacker creates a maliciously crafted .ufs, .ufs2, or .img archive file with manipulated metadata structures
2. The malicious file is delivered to the victim through social engineering, email attachment, download, or file sharing
3. The victim opens or attempts to list the contents of the archive using NanaZip
4. The UFS parser processes the malformed file and triggers out-of-bounds memory access
5. The application crashes, hangs, or experiences heap corruption that may be further exploitable

The vulnerability affects the confidentiality of system memory (through out-of-bounds read) and availability (through crashes and hangs). The attack does not require elevated privileges but does require convincing a user to open the malicious file.

Detection Methods for CVE-2026-27711

Indicators of Compromise

• Unexpected NanaZip process crashes or hangs when opening archive files
• Presence of suspicious .ufs, .ufs2, or .img files from untrusted sources
• Application error logs indicating memory access violations or heap corruption in NanaZip

Detection Strategies

• Monitor for NanaZip application crashes, particularly when associated with UFS file type operations
• Implement file type filtering or scanning for UFS/UFS2/IMG files received from external sources
• Deploy endpoint detection and response (EDR) solutions to identify abnormal process behavior patterns

Monitoring Recommendations

• Enable crash dump collection for NanaZip processes to aid in forensic analysis
• Monitor file system activity for newly created or downloaded .ufs, .ufs2, and .img files
• Review endpoint security logs for NanaZip-related memory access violations or unexpected terminations

How to Mitigate CVE-2026-27711

Immediate Actions Required

• Update NanaZip to version 6.0.1638.0 or 6.5.1638.0 or later immediately
• Avoid opening UFS, UFS2, or IMG archive files from untrusted or unknown sources
• Implement user awareness training regarding the risks of opening files from untrusted sources

Patch Information

NanaZip versions 6.0.1638.0 and 6.5.1638.0 contain the fix for this vulnerability. Users should update to one of these patched versions or later to remediate the issue. The fix addresses the boundary validation issue in the UFS parser to prevent out-of-bounds memory access when processing malformed archive files.

For additional details, refer to the GitHub Security Advisory.

Workarounds

• Until patching is possible, consider temporarily disabling or restricting access to UFS/UFS2/IMG file handling functionality
• Configure email and web gateways to quarantine or block .ufs, .ufs2, and .img file attachments from external sources
• Use alternative archive utilities for UFS file operations until NanaZip can be updated