CVE-2026-55206
py7zr: O(n^2) algorithmic complexity DoS in PackInfo._read()
- State
- Published
- Severity
- 8.7 High
- Published
- Jul 8, 2026
- Updated
- Jul 9, 2026
- Reserved
- Jun 16, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | 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 | GitHub_M |
Weaknesses
- CWE-407 Inefficient Algorithmic Complexity
Affected Products
| Product | Versions |
|---|---|
py7zrmiurahr |
|
References
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