bit7z is a cross-platform C++ static library designed for compressing and extracting archive files. Versions prior to 4.0.11 contain a path traversal vulnerability (CWE-22) in the archive extraction functionality, commonly known as a "Zip Slip" flaw. The vulnerability arises because bit7z does not properly validate or sanitize file paths within archive entries before extraction. Specifically, three exploitation vectors exist: relative path traversal (e.g., '../' sequences), absolute path traversal (e.g., paths starting with '/'), and symbolic link traversal that can redirect extraction outside the intended directory. An attacker can craft a malicious archive containing such paths and trick an application using bit7z to extract it. When the vulnerable extraction code processes these entries, files can be written arbitrarily anywhere on the filesystem accessible by the process. This arbitrary file write can overwrite application binaries, configuration files, or other sensitive files, undermining system integrity and potentially enabling further compromise. The vulnerability does not directly expose file contents, so confidentiality impact is limited to the behavior of the application after extraction. However, if the application serves or displays extracted files, attacker-created symbolic links may cause indirect confidentiality breaches. Exploitation requires user interaction to extract the malicious archive and local or delegated privileges to run the extraction. The vulnerability has a CVSS 3.1 base score of 5.5 (medium severity), reflecting the need for user interaction and local vector but significant integrity impact. The issue is addressed in bit7z version 4.0.11 by properly validating and restricting extraction paths. Until upgrading is feasible, users should implement manual path validation to ensure extracted files remain within the intended directory, run extraction processes with least privilege, and perform extraction within sandboxed or isolated directories to contain potential damage.

The primary impact of this vulnerability is the arbitrary file write capability during archive extraction, which can lead to overwriting critical application binaries, configuration files, or other sensitive data. This compromises the integrity of affected systems and may facilitate further attacks such as privilege escalation or persistent backdoors. Although confidentiality is not directly compromised by the vulnerability itself, secondary confidentiality risks exist if attacker-controlled symbolic links cause sensitive files to be exposed when served or displayed by the application. Availability impact is minimal as the vulnerability does not directly cause denial of service. Organizations that use bit7z in applications that process untrusted archives are at risk, especially if extraction is performed with elevated privileges or without proper sandboxing. This can affect software supply chains, automated processing systems, or user-facing applications that decompress archives. The requirement for user interaction and local access limits remote exploitation but does not eliminate risk in environments where users handle untrusted archives. Overall, the vulnerability can lead to significant integrity breaches and potential downstream confidentiality issues, impacting organizational security posture and trust in affected software.

1. Upgrade bit7z to version 4.0.11 or later, where the vulnerability is fixed with proper path validation. 2. If immediate upgrade is not possible, implement manual validation of each archive entry's destination path before extraction to ensure it remains within the intended extraction directory. 3. Perform archive extraction with the least privileges possible, avoiding running extraction processes as administrators or root. 4. Extract untrusted archives in sandboxed or isolated directories that do not contain sensitive files or binaries, limiting potential damage from arbitrary writes. 5. Monitor and audit extraction directories for unexpected files or symbolic links that could indicate exploitation attempts. 6. Educate users and developers about the risks of extracting archives from untrusted sources and enforce policies to restrict such actions. 7. Consider integrating additional security controls such as filesystem access controls or containerization to further isolate extraction processes. 8. Review application logic that serves or displays extracted files to ensure it safely handles symbolic links and does not inadvertently expose sensitive data.