CVE-2026-55206: CWE-407: Inefficient Algorithmic Complexity in miurahr py7zr
CVE-2026-55206 is a high-severity vulnerability in the py7zr Python library prior to version 1.1.3. The issue involves an inefficient algorithmic complexity (CWE-407) in the PackInfo._read() function, which uses an O(n^2) cumulative sum pattern on attacker-controlled input. This can cause excessive CPU consumption when processing a crafted .7z archive during initialization before extraction. The vulnerability is fixed in py7zr version 1.1.3.
AI Analysis
Technical Summary
The py7zr library, used for handling 7zip archives in Python, contained an inefficient algorithmic implementation in the PackInfo._read() method within archiveinfo.py. Specifically, the method used an O(n^2) cumulative sum pattern on the numstreams value parsed from archive headers, which can be controlled by an attacker via a crafted .7z archive. This leads to excessive CPU usage during the SevenZipFile.init() process before extraction, potentially causing a denial of service due to resource exhaustion. The issue is addressed by updating to py7zr version 1.1.3, where the inefficient algorithmic pattern is corrected.
Potential Impact
An attacker can craft a malicious .7z archive that triggers excessive CPU consumption during archive initialization in vulnerable versions of py7zr. This can lead to denial of service conditions by exhausting processing resources. There is no indication of privilege escalation, data corruption, or code execution from the provided data.
Mitigation Recommendations
Upgrade py7zr to version 1.1.3 or later, where this inefficient algorithmic complexity issue is fixed. No other mitigation or temporary workaround is indicated in the available data.
CVE-2026-55206: CWE-407: Inefficient Algorithmic Complexity in miurahr py7zr
Description
CVE-2026-55206 is a high-severity vulnerability in the py7zr Python library prior to version 1.1.3. The issue involves an inefficient algorithmic complexity (CWE-407) in the PackInfo._read() function, which uses an O(n^2) cumulative sum pattern on attacker-controlled input. This can cause excessive CPU consumption when processing a crafted .7z archive during initialization before extraction. The vulnerability is fixed in py7zr version 1.1.3.
CVSS v4.0
Score 8.7high
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The py7zr library, used for handling 7zip archives in Python, contained an inefficient algorithmic implementation in the PackInfo._read() method within archiveinfo.py. Specifically, the method used an O(n^2) cumulative sum pattern on the numstreams value parsed from archive headers, which can be controlled by an attacker via a crafted .7z archive. This leads to excessive CPU usage during the SevenZipFile.init() process before extraction, potentially causing a denial of service due to resource exhaustion. The issue is addressed by updating to py7zr version 1.1.3, where the inefficient algorithmic pattern is corrected.
Potential Impact
An attacker can craft a malicious .7z archive that triggers excessive CPU consumption during archive initialization in vulnerable versions of py7zr. This can lead to denial of service conditions by exhausting processing resources. There is no indication of privilege escalation, data corruption, or code execution from the provided data.
Mitigation Recommendations
Upgrade py7zr to version 1.1.3 or later, where this inefficient algorithmic complexity issue is fixed. No other mitigation or temporary workaround is indicated in the available data.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-16T16:16:32.627Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a4eb690c9d9e3dbe3b68734
Added to database: 07/08/2026, 20:44:00 UTC
Last enriched: 07/08/2026, 20:58:37 UTC
Last updated: 07/08/2026, 20:58:37 UTC
Views: 3
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