CVE-2001-1269 in UnZip
Summary
by MITRE
Info-ZIP UnZip 5.42 and earlier allows attackers to overwrite arbitrary files during archive extraction via filenames in the archive that begin with the / (slash) character.
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Analysis
by VulDB Data Team • 06/13/2019
The vulnerability described in CVE-2001-1269 represents a critical directory traversal flaw within the Info-ZIP UnZip utility version 5.42 and earlier. This issue stems from insufficient input validation during archive extraction processes where the software fails to properly sanitize filenames that begin with the forward slash character. The vulnerability exists in the core file extraction logic that does not adequately verify or normalize path components before writing files to the target filesystem. Attackers can exploit this weakness by crafting malicious archive files containing filenames that start with slash characters, which effectively bypasses normal directory restrictions and allows arbitrary file overwrites.
The technical implementation of this vulnerability involves the manipulation of path resolution logic within the UnZip utility. When processing archive entries, the software interprets filenames beginning with slash characters as absolute paths rather than relative paths, enabling attackers to specify arbitrary locations on the target system. This flaw falls under the category of improper input validation and path manipulation, which aligns with CWE-22 - Improper Limitation of a Pathname to a Restricted Directory. The vulnerability specifically affects the extraction routine where the software does not properly canonicalize or validate the full path before creating or overwriting files. This weakness creates a direct path traversal attack vector that can be exploited through the standard archive extraction workflow.
The operational impact of this vulnerability extends beyond simple file overwrites to potentially enable more sophisticated attacks including privilege escalation, system compromise, and persistent backdoor installation. An attacker who can upload a malicious archive file can leverage this vulnerability to overwrite critical system files, configuration files, or executable components, potentially leading to complete system compromise. The attack requires minimal privileges to execute since it only requires the ability to create or modify archive files and initiate the extraction process. This makes the vulnerability particularly dangerous in environments where users can upload files or where automated extraction processes are in place. The vulnerability also aligns with ATT&CK technique T1059 - Command and Scripting Interpreter and T1074 - Data Staged, as it enables attackers to establish persistence and manipulate system components through file overwrites.
Mitigation strategies for this vulnerability include immediate patching of UnZip utilities to versions 5.43 and later where the path validation has been corrected. System administrators should implement strict file validation policies for archive files, particularly those that may be uploaded or processed automatically. The recommended approach involves enforcing proper path normalization and validation during archive extraction, ensuring that all filenames are checked against a whitelist of allowed characters and path components. Organizations should also implement network segmentation and access controls to limit the potential impact of successful exploitation. Additional protective measures include monitoring for unusual file modification patterns, implementing file integrity checking mechanisms, and conducting regular security assessments of archive processing systems. The vulnerability demonstrates the critical importance of proper input validation in archive handling utilities and highlights the need for comprehensive security testing of file manipulation components within operating systems and applications.