High 8.7Published Jul 8, 2026

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

Updated under an hour ago (Oct 27, 2026, 10:40 AM ET)

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Every CVE for miurahr py7zr

Exploited in the last 30 days

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.

CVSS: 8.7 HIGH (v4.0, 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
Weakness (CWE): CWE-407
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Jul 9, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

miurahr py7zr miurahr:py7zr (from the name)	before 1.1.3	CNA record

References

References

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

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.