CVE-2025-61728 in archive-zip
Summary
by MITRE • 01/28/2026
archive/zip uses a super-linear file name indexing algorithm that is invoked the first time a file in an archive is opened. This can lead to a denial of service when consuming a maliciously constructed ZIP archive.
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Analysis
by VulDB Data Team • 07/06/2026
The vulnerability identified as CVE-2025-61728 resides within the archive/zip library implementation where a super-linear file name indexing algorithm is employed during the initial access to files within a ZIP archive. This algorithm exhibits exponential or quadratic time complexity behavior when processing file names, creating a significant performance degradation that can be exploited for denial of service attacks. The flaw manifests specifically during the first opening operation of any file within a maliciously crafted archive, making it particularly dangerous for systems that process untrusted ZIP files without proper sanitization measures.
The technical implementation of this vulnerability stems from inefficient indexing mechanisms that scale super-linearly with the number of files in the archive. When a ZIP archive contains a large number of entries, the algorithm's computational complexity grows at a rate faster than linear, potentially leading to extended processing times that can span several seconds or even minutes. This behavior creates a predictable resource exhaustion scenario where an attacker can construct a ZIP file with carefully crafted file names and entry counts to trigger the problematic code path. The vulnerability directly maps to CWE-778 insufficient logging, as the system fails to properly account for the computational overhead during file name processing, and can be classified under ATT&CK technique T1499.004 for resource exhaustion through malicious file processing.
The operational impact of this vulnerability extends beyond simple performance degradation to encompass complete system availability compromise. Systems that rely on archive/zip libraries for processing user-uploaded content, automated file extraction, or batch processing operations become vulnerable to sustained denial of service attacks. An attacker can construct a single malicious ZIP file that will cause any system using the affected library to experience extended processing times, potentially blocking legitimate operations and consuming excessive CPU resources. This vulnerability is particularly concerning for web applications, automated backup systems, and any service that accepts ZIP file uploads from untrusted sources. The exploitation requires minimal technical expertise as the attacker only needs to create a specially crafted archive with a specific number of entries to trigger the super-linear behavior.
Mitigation strategies for CVE-2025-61728 should focus on both immediate defensive measures and long-term architectural improvements. Organizations should implement strict file size and entry count limits when processing ZIP archives, combined with timeout mechanisms that prevent indefinite processing of suspicious files. The affected library should be updated to a patched version that employs more efficient indexing algorithms with linear or logarithmic complexity. Additionally, implementing proper input validation and sanitization measures can help detect and reject maliciously constructed archives before they reach the vulnerable code path. System administrators should monitor for unusual processing patterns and implement rate limiting on file processing operations to prevent abuse. The solution aligns with security best practices outlined in NIST SP 800-160 for software security assurance and follows the principle of least privilege by limiting the computational resources available to archive processing operations.