Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-08T20:30:58 py7zr: py7zr: Denial of Service via decompression bomb in 7zip archive extraction 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H CWE-409

py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Prior to 1.1.3, py7zr's Worker.decompress() extracted archive entries without tracking total decompressed size, allowing a crafted .7z file such as a 15.6 KB archive that expands to 100 MB to exhaust disk or memory before extraction completes. This issue is fixed in version 1.1.3.

A flaw was found in py7zr, a Python library for 7zip archive handling. This vulnerability allows a remote attacker to cause a Denial of Service (DoS) by providing a specially crafted .7z file. The `Worker.decompress()` function fails to track the total decompressed size, enabling a small archive to expand significantly and exhaust system resources such as disk space or memory during extraction. This issue is also known as a decompression bomb (CWE-409).

This Moderate impact flaw in the py7zr Python library can lead to a denial of service when processing specially crafted 7zip archives. An attacker could provide a malicious archive that, upon decompression, exhausts system resources such as disk space or memory, impacting the availability of services that utilize py7zr for archive handling. Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. https://www.cve.org/CVERecord?id=CVE-2026-55195 https://nvd.nist.gov/vuln/detail/CVE-2026-55195 https://github.com/miurahr/py7zr/commit/28faf107b64374fa5a02bfb93aa2024e281ca97b https://github.com/miurahr/py7zr/releases/tag/v1.1.3 https://github.com/miurahr/py7zr/security/advisories/GHSA-gjrg-mpp7-g774