fstream fstream.DirWriter() Function Arbitrary File Overwrite Vulnerability [CVE-2019-13173]

CVE number – CVE-2019-13173

A vulnerability in fstream could allow an unauthenticated, remote attacker to overwrite arbitrary files on a targeted system.

The vulnerability exists in the fstream.DirWriter() function of the affected software. If the software extracts tarballs containing a hardlink to a file that already exists in the system, the file could be overwritten with the contents of the extracted file if the file on the system matches the hardlink.

An attacker could exploit this vulnerability to by sending a tarball that submits malicious input to the targeted system. A successful exploit could allow the attacker to overwrite arbitrary files on the system, which could be used to conduct further attacks. 

The vendor has confirmed the vulnerability and released software updates.

Analysis

• To exploit this vulnerability, an attacker may need access to the same internal network where the targeted system resides to send a tarball that submits malicious input to the targeted system.

Safeguards

• Administrators are advised to apply the appropriate updates.
  
  Administrators are advised to allow only trusted users to have network access.
  
  Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.
  
  Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
  
  Administrators can help protect affected systems from external attacks by using a solid firewall strategy.
  
  Administrators are advised to monitor affected systems.

Vendor Announcements

• The vendor has released a git commit at the following link: commit 7ecef07da6a9e72cc0c4d0c9c6a8e85b6b52395d

Fixed Software

• The vendor has released software updates at the following link: fstream 1.0.12