{"id":"CVE-2026-55206","aliases":["GHSA-h4gh-22qq-72r7","PYSEC-2026-2973"],"url":"https://o3.security/vulnerability/CVE-2026-55206","summary":"py7zr: O(n^2) algorithmic complexity DoS in PackInfo._read()","details":"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.","published":"2026-07-08T20:32:09.905Z","modified":"2026-08-12T03:51:44.548004557Z","cvss":null,"epss":{"score":0.0021,"percentile":0.11492,"asOf":"2026-08-22"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"py7zr","fixedVersion":"1.1.3"}],"fix":{"url":"https://github.com/miurahr/py7zr/commit/d7aa3a197d15c75a65b24f796d3a69f83806d3f8","label":"miurahr/py7zr@d7aa3a1"},"references":[{"type":"WEB","url":"https://github.com/miurahr/py7zr/releases/tag/v1.1.3"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55206.json"},{"type":"ADVISORY","url":"https://github.com/miurahr/py7zr/security/advisories/GHSA-h4gh-22qq-72r7"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55206"},{"type":"FIX","url":"https://github.com/miurahr/py7zr/commit/d7aa3a197d15c75a65b24f796d3a69f83806d3f8"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:44.548004557Z"}}