Arbitrary file write via crafted symbolic links during archive extraction

Summary

py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Versions 1.1.2 and below contain an an arbitrary file write vulnerability, which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using extractall to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service. This issue has been fixed in version 1.1.3. A flaw was found in py7zr. An attacker can craft a malicious archive containing symbolic links that, when extracted, can lead to arbitrary file writes outside the intended directory. This vulnerability may allow for remote code execution, privilege escalation, data corruption, or denial of service. This flaw has an Important impact as py7zr shipped in Red Hat Ansible Automation Hub is susceptible to arbitrary file writes during archive extraction. An attacker can craft a malicious 7zip archive containing symbolic link chains that resolve outside the intended extraction directory, bypassing path validation. When a user or automated pipeline extracts the archive using py7zr's extractall method, subsequent files can be written to arbitrary locations on the filesystem, potentially leading to remote code execution or data corruption. Red Hat severity: Important — CVSS 8 (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H). Weakness: CWE-22. No fixing RHSA erratum has published yet; monitor the Red Hat CVE page and patch when it ships.