CVE-2026-23879: CWE-59: Improper Link Resolution Before File Access ('Link Following') in miurahr py7zr
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.
AI Analysis
Technical Summary
The py7zr Python library (version 1.1.2 and earlier) improperly resolves symbolic links during the extractall operation. It only verifies that the link's arcname is within the destination directory but fails to resolve the full symlink path, allowing malicious archives to recreate symbolic links pointing outside the extraction directory. This can lead to arbitrary file writes when files are extracted through these links, potentially causing remote code execution, privilege escalation, data corruption, or denial of service. The issue is tracked as CVE-2026-23879 and is classified under CWE-59 (Improper Link Resolution Before File Access). The vulnerability is fixed in py7zr version 1.1.3.
Potential Impact
Successful exploitation allows attackers to write files outside the intended extraction directory by abusing symbolic link chains, which can lead to remote code execution, privilege escalation, data corruption, or denial of service on the affected system.
Mitigation Recommendations
Upgrade py7zr to version 1.1.3 or later, where this vulnerability has been fixed. No other mitigations are specified. Patch status is confirmed fixed in version 1.1.3.
CVE-2026-23879: CWE-59: Improper Link Resolution Before File Access ('Link Following') in miurahr py7zr
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.
CVSS v3.1
Score 8.0high
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The py7zr Python library (version 1.1.2 and earlier) improperly resolves symbolic links during the extractall operation. It only verifies that the link's arcname is within the destination directory but fails to resolve the full symlink path, allowing malicious archives to recreate symbolic links pointing outside the extraction directory. This can lead to arbitrary file writes when files are extracted through these links, potentially causing remote code execution, privilege escalation, data corruption, or denial of service. The issue is tracked as CVE-2026-23879 and is classified under CWE-59 (Improper Link Resolution Before File Access). The vulnerability is fixed in py7zr version 1.1.3.
Potential Impact
Successful exploitation allows attackers to write files outside the intended extraction directory by abusing symbolic link chains, which can lead to remote code execution, privilege escalation, data corruption, or denial of service on the affected system.
Mitigation Recommendations
Upgrade py7zr to version 1.1.3 or later, where this vulnerability has been fixed. No other mitigations are specified. Patch status is confirmed fixed in version 1.1.3.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-01-16T21:02:02.900Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a3c3685e60265867b7394ef
Added to database: 06/24/2026, 19:56:53 UTC
Last enriched: 07/01/2026, 22:38:37 UTC
Last updated: 08/08/2026, 00:41:11 UTC
Views: 92
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