CVE-2021-46854: Uncovering the Memory Disclosure Issue in mod

We live in a digital world where data security is of the utmost importance. With each passing day, we learn of new vulnerabilities and exploits discovered in various software packages. One such vulnerability is CVE-2021-46854, recently identified in the mod_radius authentication module of the popular File Transfer Protocol (FTP) server software, ProFTPD. This vulnerability dates up until version 1.3.7c and may lead to the disclosure of sensitive information to Remote Authentication Dial-In User Service (RADIUS) servers.

In this long-read post, we shall provide you with an in-depth analysis of this vulnerability, a code snippet illustrating the issue, links to original references, and some details about the potential exploit.

Memory Disclosure Issue in mod_radius

The mod_radius is an authentication module in ProFTPD that enables the server to authenticate clients based on a RADIUS server. This module works in conjunction with a RADIUS server conforming to the RADIUS protocol (RFC 2865).

The CVE-2021-46854 vulnerability in the mod_radius module stems from the improper management of the memory while copying password blocks. When sending the RADIUS-Password attribute to the RADIUS server, this module erroneously copies 16-character blocks, potentially leading to the disclosure of sensitive information in memory.

Here is a snippet of the problematic code in question, which can be found in the mod_radius.c source file:

while (len > ) {
  unsigned char *ptr;

  ptr = buf;
  memcpy(remote_pwd, ptr, 16); /* <-- this is the problematic copying of 16 bytes */
  ptr += 16;
  len -= 16;
}

For more details on this specific vulnerability, you can refer to the following resources

1. Original CVE Entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-46854

2. National Vulnerability Database (NVD) Entry: https://nvd.nist.gov/vuln/detail/CVE-2021-46854

3. ProFTPD's Official GitHub Repository: https://github.com/proftpd/proftpd

4. ProFTPD's Official Website: http://proftpd.org/

This memory disclosure vulnerability could be exploited by malicious actors in the following way

1. An attacker with access to the victim's RADIUS server might monitor RADIUS-Password attributes sent by the vulnerable ProFTPD server.

2. By exploiting this vulnerability, the attacker might observe an extra memory disclosed in the 16-character blocks being sent.

3. This disclosure may contain sensitive information, such as user passwords, configuration settings, or other application data, which could result in security breaches or unauthorized access.

Conclusion and Recommendations

It is crucial for any network administrator or IT professional to stay up to date on security vulnerabilities and to install patches and updates as soon as they become available. To mitigate the CVE-2021-46854 vulnerability, it is recommended to update the ProFTPD server to version 1.3.7c or higher. This will help prevent potential exploits and ensure the secure operation of your FTP services.

Additionally, consider implementing measures on the RADIUS server side to strengthen its security posture and using encryption/authentication protocols to further protect sensitive information on the network. Regularly monitoring and reviewing security logs can also aid in identifying malicious activity in the network infrastructure.

In today's era of constant threats, staying vigilant and protecting your digital assets is the key to maintaining a secure digital environment.

Timeline

Published on: 11/23/2022 07:15:00 UTC
Last modified on: 05/03/2023 11:15:00 UTC