Denial of Service via crafted.7z archives due to inefficient algorithmic complexity

Summary

py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Prior to 1.1.3, PackInfo._read() in archiveinfo.py used an O(n^2) cumulative sum pattern for attacker-controlled numstreams values parsed from archive headers, allowing a crafted .7z archive to cause excessive CPU consumption during SevenZipFile.init() before extraction. This issue is fixed in version 1.1.3. A flaw was found in py7zr, a Python library for 7zip archives. A remote attacker could exploit this vulnerability by providing a specially crafted .7z archive. This archive, when processed by the `SevenZipFile.init()` function, triggers an inefficient algorithmic complexity (CWE-407) during header parsing. This leads to excessive CPU consumption, resulting in a Denial of Service (DoS) for any application that opens untrusted .7z archives using py7zr. This Moderate severity flaw in the `py7zr` library can lead to a Denial of Service. Applications that utilize `py7zr` to open or process untrusted `.7z` archives are vulnerable to excessive CPU consumption. Red Hat severity: Moderate — CVSS 6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H). Weakness: CWE-606.