CVE-2023-42465: Row Hammer Vulnerability in Sudo Before 1.9.15 - Exploit Details, Code Snippets, and Original References

CVE-2023-42465 is a critical vulnerability discovered in the popular Unix-based command line utility called Sudo. This security weakness potentially allows attackers to launch row hammer attacks and perform malicious activities such as authentication bypass and privilege escalation. This blog post aims to discuss the details of this vulnerability, showcase the code snippets related to the issue, and provide links to original resources.

Sudo, which stands for "Super-user do", is a vital Linux and Unix command that allows users to run commands as the superuser (or another user) while providing necessary authentication. The security flaw discovered in Sudo versions earlier than 1.9.15 can lead to dangerous consequences, and updating to the latest release is highly recommended.

Exploit Details

The primary cause of CVE-2023-42465 is faulty application logic. In the affected Sudo versions, the logic is set to rely on not equaling an error value, instead of equaling a success value. Additionally, the value handling process does not include proper defense mechanisms against single-bit flips, which is a method used to manipulate bits of memory.

Single-bit flips, in particular, could be exploited in row hammer attacks. Row hammer attacks involve repeated reading and writing of certain memory addresses, causing random bit flips in adjacent memory rows. A skilled attacker can potentially exploit these bit flips to gain unauthorized access and escalate privilege levels in the system using the vulnerable Sudo version.

To demonstrate the weak logic check, consider the following code snippet

/* Returns true if the error code e is "successful". */
bool handle_error(ERROR_CODE e) {
  if (e != ERROR_UNSUCCESSFUL) {
    return true;
  }
  return false;
}

The issue with this code is that it checks for the absence of an error (e != ERROR_UNSUCCESSFUL), rather than confirming success explicitly. Since other values could also be non-errors, such as a bit flip caused by row hammer, this code could potentially yield false positives.

Instead, the code should explicitly check for success

/* Returns true if the error code e is "successful". */
bool handle_error(ERROR_CODE e) {
  if (e == ERROR_SUCCESSFUL) {
    return true;
  }
  return false;
}

This updated code snippet now properly checks for success rather than the absence of one specific error, making it more robust against unexpected values such as those caused by row hammer attacks.

Original References

1. Official Sudo Security Alert: https://www.sudo.ws/alerts/row_hammer.html
2. National Vulnerability Database (NVD) entry: https://nvd.nist.gov/vuln/detail/CVE-2023-42465
3. Row Hammer Attack Wikipedia: https://en.wikipedia.org/wiki/Row_hammer

Conclusion and Mitigation

CVE-2023-42465 is a critical vulnerability rooted in weak application logic, leaving Sudo versions earlier than 1.9.15 susceptible to row hammer attacks. Users are strongly advised to update their systems to the latest version to mitigate the risk of potential breaches and unauthorized privilege escalation.

For additional security, system administrators should carefully review and set appropriate permissions for Sudo users and ensure that Sudo is installed and configured diligently. Performing regular security audits and staying up-to-date with the latest vulnerabilities will help in maintaining the safety of Unix-based systems.

Timeline

Published on: 12/22/2023 16:15:08 UTC
Last modified on: 02/18/2024 03:15:07 UTC