py7zr: O(n^2) algorithmic complexity DoS in PackInfo._read() (CVE-2026-55206) | HOL Guard CVE

High · CVSS 8.7CVE-2026-55206GHSA-H4GH-22QQ-72R7

py7zr: O(n^2) algorithmic complexity DoS in PackInfo._read()

Answer in brief

CVE-2026-55206 records a High severity (CVSS 8.7) vulnerability in py7zr: O(n^2) algorithmic complexity DoS in PackInfo._read(). The current sources do not mark it as known exploited. The current feed maps miurahr/py7zr (generic), py7zr (pip). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 8, 2026Updated Jul 10, 2026Source checked Sep 17, 2026First seen by HOL Jun 19, 2026Material review Jul 10, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.7
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps miurahr/py7zr (generic), py7zr (pip). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
miurahr/py7zrgeneric	< 1.1.3	Not reported
py7zrpip	<=1.1.2	1.1.3

Recommended response

Check inventory. Check lockfiles and deployed manifests for miurahr/py7zr, py7zr.
Review the reported fix. Update py7zr to 1.1.3 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jul 8, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Jul 10, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jun 19, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.