Shellinabox shellinaboxd Multipart/Form-data HTTP Request Denial of Service Vulnerability [CVE-2018-16789]

CVE Number – CVE-2018-16789

A vulnerability in the shellinaboxd component of Shellinabox could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on a targeted system.

The vulnerability exists in the libhttp/url.c source code file, and is due to improper resource management that is performed by the affected software when handling multipart/form-data HTTP requests. The vulnerability manifests as an infinite loop error condition. An attacker could exploit the vulnerability by sending a multipart/form-data HTTP request that submits malicious input to the affected software. A successful exploit could allow the attacker to cause the affected software to stop responding and completely consume CPU resources, resulting in a DoS condition. 

Functional code that exploits this vulnerability is publicly available. 

The Shellinabox project has confirmed the vulnerability and released software updates.

Analysis

• To exploit this vulnerability, the attacker must send a malicious request to the targeted system, making exploitation more difficult in environments that restrict network access from untrusted sources.

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 Shellinabox project has confirmed the vulnerability in a github issue and pull request at the following links: Rolling code for version 2.21 and CVE-2018-16789: fix for broken multipart/form-data #446

Fixed Software

• The Shellinabox project has published a git commit at the following link; however at the time this alert was first published the update had not yet been pushed into the master branch: Rolling code for version 2.21