CVE-2020-7664 in Google
Summary
by MITRE
The ExtractTo function doesn't securely escape file paths in zip archives which include leading or non-leading "..". This allows an attacker to add or replace files system-wide.
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Analysis
by VulDB Data Team • 10/26/2020
The vulnerability identified as CVE-2020-7664 represents a critical path traversal flaw in zip archive extraction functionality that stems from inadequate input validation and sanitization of file paths. This issue affects software systems that process zip archives and fail to properly validate or escape directory traversal sequences within archive entries, creating a pathway for arbitrary file system manipulation. The flaw specifically manifests when the ExtractTo function processes archive entries containing leading or non-leading ".." sequences that reference parent directories, allowing attackers to bypass intended extraction boundaries.
The technical implementation of this vulnerability exploits the fundamental weakness in path validation logic where the system does not adequately sanitize file paths before performing extraction operations. When zip archives contain entries with directory traversal sequences such as "../" or "/../", the vulnerable extraction function fails to properly resolve or validate these paths against the intended target directory. This results in the system treating these malicious paths as legitimate extraction targets, enabling attackers to write files to arbitrary locations on the file system. The vulnerability is particularly dangerous because it operates at the archive processing level, where legitimate software applications commonly perform automated extraction operations without proper security context validation.
From an operational perspective, this vulnerability creates significant attack surface implications for systems that process untrusted zip archives. Attackers can leverage this flaw to overwrite critical system files, inject malicious code into existing applications, or create backdoor access points within the target environment. The impact extends beyond simple file replacement to include potential privilege escalation scenarios where attackers can manipulate system configuration files or binaries that execute with elevated privileges. This vulnerability commonly affects web applications, automated deployment systems, and any software that automatically extracts zip archives from untrusted sources without proper security controls.
Security practitioners should implement multiple layers of mitigation to address this vulnerability effectively. The primary defense mechanism involves implementing robust input validation that sanitizes all file paths within archive entries by removing or escaping directory traversal sequences before extraction operations. This approach aligns with established security practices and corresponds to CWE-22 which specifically addresses path traversal vulnerabilities in software systems. Additionally, extraction operations should be performed within restricted sandboxed environments with minimal privileges, preventing attackers from gaining system-wide file system access even if they successfully exploit the vulnerability. Organizations should also consider implementing strict file path validation that ensures all extracted paths remain within the intended target directory boundaries, utilizing canonical path resolution techniques to eliminate any ambiguity in path interpretation.
The vulnerability demonstrates characteristics consistent with ATT&CK technique T1059.007 which involves executing malicious code through archive extraction processes. This classification indicates that the attack vector specifically targets automated system processes that handle archive files, making it particularly effective against systems with automated deployment or update mechanisms. Security controls should include monitoring for unusual file system access patterns during archive extraction operations and implementing network-based restrictions that prevent the download or processing of untrusted archive files from external sources. The remediation process requires comprehensive code review of all archive processing functions, implementation of secure coding practices for path validation, and regular security testing to ensure that similar vulnerabilities do not exist in other file processing components within the system architecture.