CVE-2026-55206 | py7zr is a Python-based library and utility to support 7zip … | CVSS 8.7 HIGH

Description

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.

Metadata

CVE ID: CVE-2026-55206
State: PUBLISHED
Assigner: GitHub_M
Reserved: 2026-06-16 16:16 UTC
Published: 2026-07-08 20:32 UTC
Last updated: 2026-07-09 14:26 UTC
Primary CWE: CWE-407
CWE-407: Inefficient Algorithmic Complexity
Vendor / Product: miurahr / py7zr
Sources: cve.org · NVD

Severity & Metrics

8.7 HIGH CVSS 4.0

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

SSVC — CISA Coordinator

Exploitation: PoC
Automatable: yes
Tech. Impact: partial

Affected products (1)

Vendor	Product	Platform	Versions
miurahr	py7zr	—	< 1.1.3

Weakness (CWE)

CWE	Source	Description
CWE-407	cna	CWE-407: Inefficient Algorithmic Complexity

CVSS scores (1)

Score	Severity	Version	Source	Vector
8.7	HIGH	4.0	cna	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

References (3)

https://github.com/miurahr/py7zr/security/advisories/GHSA-h4gh-22qq-72r7 https://github.com/miurahr/py7zr/security/advisories/GHSA-h4gh-22qq-72r7
https://github.com/miurahr/py7zr/commit/d7aa3a197d15c75a65b24f796d3a69f83806d3f8 https://github.com/miurahr/py7zr/commit/d7aa3a197d15c75a65b24f796d3a69f83806d3f8
https://github.com/miurahr/py7zr/releases/tag/v1.1.3 https://github.com/miurahr/py7zr/releases/tag/v1.1.3