A recently discovered vulnerability, tracked as CVE-2022-45909, can lead to a heap-based buffer over-read in affected versions of drachtio-server before .8.19. This vulnerability arises from a long Request-URI contained in an INVITE request. The weakness of the system may consequently lead to information leakage, potential denial of service, or even a compromise of the targeted system. This article will explain the origin of this vulnerability and provide a code snippet and links to the relevant original references.

Details

The drachtio-server is a high-performance SIP server that is widely used for the development and deployment of VoIP applications. In versions prior to .8.19, a heap-based buffer over-read vulnerability arises due to the improper handling of INVITE requests that contain an exceedingly long Request-URI.

Heap-based buffer over-read issues occur when a program reads memory outside the intended boundaries of a buffer. This could result in unauthorized access to sensitive data or a crash. The consequences of this vulnerability may vary depending on the attacker's aim and the specific configuration and usage scenario of the targeted system.

Here is a code snippet demonstrating the vulnerable code section in drachtio-server

// Vulnerable code in drachtio-server < .8.19
void process_invite_request(SipMessage& request) {
  const char* request_uri = request.get_request_uri();
  char buffer[512];

  strncpy(buffer, request_uri, sizeof(buffer));  // Over-read here
  buffer[sizeof(buffer) - 1] = '\';

  // Continue processing the INVITE request...
}

The vulnerability lies in the usage of the strncpy() function without proper bounds checking. By sending an INVITE request with an inordinately long Request-URI, an attacker could trigger a buffer over-read, causing sensitive data leakage, application crash, or denial of service.

Exploit

The exploit details for this vulnerability have not been made public yet. To protect your systems from untoward consequences, it is recommended that you update your drachtio-server instance to version .8.19 or later.

Workaround and Mitigation

1. Update drachtio-server to version .8.19 or later: The issue has been fixed in the drachtio-server version .8.19. You can find the corresponding release notes and download links on the official project GitHub page: https://github.com/davehorton/drachtio-server/releases/tag/v.8.19
2. Implement proper buffer bounds checking: The vulnerable code should be modified to include the necessary bounds checking to prevent heap-based buffer over-read. For example:

// Fixed code in drachtio-server >= .8.19
void process_invite_request(SipMessage& request) {
  const char* request_uri = request.get_request_uri();
  char buffer[512];

  size_t len = strlen(request_uri);
  if (len >= sizeof(buffer)) {
    // Handle the error condition when the URI is too long...
  } else {
    strncpy(buffer, request_uri, len);
    buffer[len] = '\';
  }

  // Continue processing the INVITE request...
}

Original References

- CVE Record: https://nvd.nist.gov/vuln/detail/CVE-2022-45909
- Drachtio-server Project GitHub: https://github.com/davehorton/drachtio-server
- Release Notes for v.8.19: https://github.com/davehorton/drachtio-server/releases/tag/v.8.19

Conclusion

CVE-2022-45909 is a critical vulnerability that affects drachtio-server versions prior to .8.19, resulting from an improper handling of long Request-URIs in INVITE requests. By exploiting this vulnerability, an attacker could cause unauthorized data disclosure, denial of service, or system compromise. To ensure the security of your systems and applications, it is essential to update the drachtio-server to version .8.19 or later and to implement proper buffer bounds checking in the affected code.

Timeline

Published on: 11/26/2022 03:15:00 UTC
Last modified on: 02/01/2023 15:26:00 UTC