miurahr py7zr up to 1.1.2 Archive Info archiveinfo.py PackInfo._read numstreams resource consumption

Summaryinfo

A vulnerability identified as problematic has been detected in miurahr py7zr up to 1.1.2. This impacts the function PackInfo._read of the file archiveinfo.py of the component Archive Info Handler. Performing a manipulation of the argument numstreams results in resource consumption. This vulnerability is identified as CVE-2026-55206. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability classified as problematic has been found in miurahr py7zr up to 1.1.2. This affects the function PackInfo._read of the file archiveinfo.py of the component Archive Info Handler. The manipulation of the argument numstreams with an unknown input leads to a resource consumption vulnerability. CWE is classifying the issue as CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. This is going to have an impact on availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-55206 since 06/16/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 1.1.3 eliminates this vulnerability.

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Productinfo

Vendor

• miurahr

Name

• py7zr

Version

• 1.1.0
• 1.1.1
• 1.1.2

Website

• Product: https://github.com/miurahr/py7zr/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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