CVE-2023-51713: Understanding make_ftp_cmd Out-Of-Bounds Read and ProFTPD Daemon Crash Vulnerability in Versions Before 1.3.8a

The Common Vulnerabilities and Exposures (CVE) system identifies a vulnerability in ProFTPD before version 1.3.8a with the CVE identifier "CVE-2023-51713". This post will discuss the details of CVE-2023-51713, including a code snippet and links to original references to help you understand the issue and how it could be exploited. Our goal is to provide clear and concise information about the vulnerability and its impact using simple American English.

Background on ProFTPD

ProFTPD is a widely used, open-source FTP server that is known for its high level of performance, security, and configurability. Nonetheless, software vulnerabilities are common, and ProFTPD is no exception. In this case, the vulnerability in question is related to the "make_ftp_cmd" function found within the main.c source file. This vulnerability can result in a daemon crash and a one-byte out-of-bounds read.

Details of the Vulnerability

As mentioned earlier, the vulnerability exists within the "make_ftp_cmd" function in the main.c file of ProFTPD. The issue is caused by the improper handling of quote and backslash semantics, which can potentially lead to a daemon crash and the aforementioned one-byte out-of-bounds read.

Here is the affected code snippet

for (i = ; cmd[i]; i++) {
  /* Escape any quote (") character. */
  if (cmd[i] == '\"') {
    tmp[j++] = '\\';
  }

  tmp[j++] = cmd[i];
}

The problem arises due to the mishandling of the quote (") and backslash (\) characters. As a result, the "tmp" variable will point one byte ahead of the assigned buffer when one of these characters is encountered, causing a one-byte out-of-bounds read. This, in turn, can lead to a daemon crash.

Exploiting this Vulnerability

An attacker could potentially exploit this vulnerability by crafting a malicious FTP command or argument, which triggers the code snippet mentioned earlier. When the "make_ftp_cmd" function attempts to process this command or argument, the one-byte out-of-bounds read will occur, which could lead to a crash of the FTP server daemon. This crash could, in turn, lead to a denial of service (DoS) condition where the FTP server is temporarily unable to respond to client requests.

It's important to note that the severity of the vulnerability is relatively low, as it only results in crashing the FTP server daemon, and no remote code execution or privilege escalation occurs as a direct result of this vulnerability.

Mitigation

To address this vulnerability, the developers of ProFTPD released version 1.3.8a that includes a patch for the make_ftp_cmd issue. Users are encouraged to update their ProFTPD installations to version 1.3.8a or later to protect themselves from potential exploitation.

Links to Original References

1. CVE-2023-51713: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-51713
2. Source file main.c (ProFTPD GitHub): https://github.com/proftpd/proftpd/blob/1.3.7a/contrib/main.c
3. ProFTPD 1.3.8a changelog: https://github.com/proftpd/proftpd/blob/1.3.8a/NEWS

Conclusion

In summary, CVE-2023-51713 is a low-severity vulnerability that affects ProFTPD FTP servers running versions before 1.3.8a. This vulnerability can potentially be exploited, leading to a daemon crash and denial of service conditions. To mitigate this issue, users should update their ProFTPD installations to version 1.3.8a or later to prevent any potential exploits.

Timeline

Published on: 12/22/2023 03:15:09 UTC
Last modified on: 01/08/2024 19:06:50 UTC