CVE-2026-17524 in zip-lib
Summary
by MITRE • 07/28/2026
Versions of the package zip-lib before 1.1.0 are vulnerable to Directory Traversal via the caching mechanism for path validation during the extraction process. An attacker can bypass security checks designed to prevent directory traversal. The intended security function, isOutsideTargetFolder, only checks and caches the path status when the initial directory symlink is created during the first extraction.
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Analysis
by VulDB Data Team • 07/28/2026
The vulnerability in zip-lib versions prior to 1.1.0 represents a critical directory traversal flaw that undermines fundamental security controls designed to protect against unauthorized file system access. This issue stems from a flawed caching mechanism within the package's path validation logic, specifically affecting how the isOutsideTargetFolder function operates during extraction processes. The vulnerability manifests when attackers exploit the incomplete validation approach that only evaluates and caches path status during the initial directory symlink creation phase, leaving subsequent extractions vulnerable to bypass attacks.
The technical implementation of this flaw involves a race condition between the caching mechanism and actual path validation. During the first extraction operation, the isOutsideTargetFolder function performs its security check and caches the result for future reference. However, this cached validation becomes ineffective when subsequent operations attempt to extract files that might have been modified or when symbolic links are created that bypass the initial validation checks. The vulnerability creates a persistent security gap where attackers can manipulate file paths to traverse outside of intended target directories, potentially gaining access to sensitive system resources or executing arbitrary code.
From an operational impact perspective, this directory traversal vulnerability exposes systems using zip-lib to significant risks including unauthorized data access, privilege escalation, and potential system compromise. Attackers could leverage this flaw to extract files to arbitrary locations on the file system, potentially overwriting critical system files or accessing restricted directories containing sensitive information. The vulnerability is particularly dangerous in environments where zip-lib is used for processing untrusted archive files, such as web applications handling user-uploaded content or automated systems processing external data sources.
The security implications of this vulnerability align with common weakness enumerations classified under CWE-22 Directory Traversal and CWE-352 Cross-Site Request Forgery, representing a combination of path manipulation and access control bypass techniques. From an attack framework perspective, this vulnerability maps to ATT&CK technique T1059 Command and Scripting Interpreter and T1566 Phishing with Malicious Attachments, as it enables attackers to execute malicious code through compromised archive files. The mitigation strategy requires immediate patching to version 1.1.0 or later where the caching mechanism has been properly redesigned to validate paths on each extraction operation rather than relying on potentially stale cached results.
Organizations should implement comprehensive monitoring for suspicious file extraction activities and consider deploying additional layers of protection including network segmentation, file access controls, and regular security audits of systems using vulnerable versions. The vulnerability highlights the importance of proper validation caching mechanisms and demonstrates how seemingly minor implementation details can create significant security weaknesses in widely-used libraries. System administrators must prioritize updating affected installations and conducting thorough security assessments to identify any potential exploitation attempts that may have occurred prior to patching.