CVE-2023-31130: Buffer Underflow Vulnerability Found in C-ares Asynchronous Resolver Library

Recently, a CVE (Common Vulnerabilities and Exposures) identified as CVE-2023-31130 has been reported for the c-ares resolver library, which is commonly used for asynchronous Domain Name System (DNS) operations. This article will provide an in-depth analysis of the vulnerability, along with its potential impact and links to the original sources.

Context

C-ares is an asynchronous resolver library designed to handle DNS queries effectively. The library allows applications to perform DNS queries without blocking, thus enabling better performance.

Vulnerability: CVE-2023-31130
A vulnerability has been identified in the c-ares resolver library, which could result in buffer underflow for certain IPv6 addresses. The vulnerability is related to the ares_inet_net_pton() function, which is found to cause issues when handling addresses like "::00:00:00/2."

Exploitable Code Snippet

The code snippet below demonstrates the vulnerability in the ares_inet_net_pton() function.

#include <ares.h>
#include <arpa/inet.h>
#include <stdio.h>

int main() {
  struct ares_in6_addr in6;
  int result = ares_inet_net_pton(AF_INET6, "::00:00:00/2", &in6, sizeof(in6));
  if(result > ) {
    printf("Successfully parsed IPv6 address.\n");
  } else {
    printf("Error occurred in parsing IPv6 address: %d\n", result);
  }
  return ;
}

External Exploits

Though the c-ares library uses the ares_inet_net_pton() function internally for configuration purposes, users who utilize this function externally for other tasks might encounter problems when dealing with specific IPv6 addresses.

Original References

The c-ares project has acknowledged this vulnerability and provided an official fix in version 1.19.1. The original reference to this issue can be found in their GitHub repository here: c-ares/c-ares#411

Fix:
If you are using the ares_inet_net_pton() function either internally or externally, it is highly recommended to update the c-ares library to version 1.19.1 or newer. This updated version contains the necessary fix for addressing this vulnerability.

The link to download the fixed version is as follows

c-ares 1.19.1

Conclusion

CVE-2023-31130 is a buffer underflow vulnerability present in the c-ares asynchronous resolver library. This vulnerability affects the ares_inet_net_pton() function and can be triggered when handling certain IPv6 addresses.

While the impact of this vulnerability might be limited in default implementations of the library, users who utilize the function in their code must update their library to version 1.19.1 or newer to mitigate the risk.

Always stay vigilant and ensure that you are using updated and secure software libraries in your projects to minimize the risk of potential vulnerabilities.

Timeline

Published on: 05/25/2023 22:15:00 UTC
Last modified on: 06/26/2023 22:15:00 UTC