CVE-2026-55206

CVE-2026-55206 is a high-severity vulnerability with a CVSS 4.0 base score of 8.7. The underlying weakness is classified as CWE-407.

Key facts

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-55206?
CVE-2026-55206 has a CVSS 4.0 base score of 8.7, rated high severity.
Is CVE-2026-55206 being actively exploited?
It is not currently listed in CISA's Known Exploited Vulnerabilities catalog, and no EPSS exploit-prediction score is available yet.
How do I fix CVE-2026-55206?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-55206 published?
CVE-2026-55206 was published on 2026-07-08.

References

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