Mobile Security Framework (MobSF) Allows Web Server Resource Exhaustion via ZIP of Death Attack

Summary

MobSF is a mobile application security testing tool used. Typically, MobSF is deployed on centralized internal or cloud-based servers that also host other security tools and web applications. Access to the MobSF web interface is often granted to internal security teams, audit teams, and external vendors. MobSF provides a feature that allows users to upload ZIP files for static analysis. Upon upload, these ZIP files are automatically extracted and stored within the MobSF directory. However, in versions up to and including 4.3.2, this functionality lacks a check on the total uncompressed size of the ZIP file, making it vulnerable to a ZIP of Death (zip bomb) attack. Due to the absence of safeguards against oversized extractions, an attacker can craft a specially prepared ZIP file that is small in compressed form but expands to a massive size upon extraction. Exploiting this, an attacker can exhaust the server's disk space, leading to a complete denial of service (DoS) not just for MobSF, but also for any other applications or websites hosted on the same server. This vulnerability can lead to complete server disruption in an organization which can affect other internal portals and tools too (which are hosted on the same server). If some organization has created their customized cloud based mobile security tool using MobSF core then an attacker can exploit this vulnerability to crash their servers. Commit 6987a946485a795f4fd38cebdb4860b368a1995d fixes this issue. As an additional mitigation, it is recommended to implement a safeguard that checks the total uncompressed size of any uploaded ZIP file before extraction. If the estimated uncompressed size exceeds a safe threshold (e.g., 100 MB), MobSF should reject the file and notify the user.