CVE-2026-55206

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 4.0

8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

EPSS

0.3% chance of exploitation in the next 30 days; higher than 24% of CVEs (scores of 2026-10-25)

CWE

CWE-407

Published

2026-07-08

Modified

2026-10-25

Record from

the NVD, synced 2026-10-25

Packages (OSV)

References

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

Check your stackJSON