A new vulnerability, CVE-2023-2906, has recently been discovered in Wireshark, a widely used network protocol analyzer. This vulnerability is a result of improper validation of the length provided by an attacker-crafted CP2179 packet. Affected Wireshark versions range from 2.. to 4..7, and it enables a divide by zero, which can lead to a denial of service attack.

In this blog post, we will provide a detailed breakdown of the vulnerability, a code snippet to demonstrate its exploit, links to original references for further reading, and suggestions for mitigating the risk posed by this vulnerability.

Technical Background

A CP2179 packet, associated with the CP2179 protocol, is designed to provide a method for transmitting data and commands between devices on a network. Due to a failure to validate the length provided by the packet, Wireshark's implementation of CP2179 is susceptible to a divide by zero error.

A divide by zero error occurs when a number is divided by zero. In this case, the resultant infinite value is undefined. An attacker can exploit this error to cause a Denial of Service (DoS) attack on the network by creating a malicious packet with a zero-length, forcing the Wireshark application to crash.

Here's an example of a vulnerable code snippet

void dissect_cp2179(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
  guint32 length;
  guint32 divisor;

  // Get the packet length
  length = tvb_get_ntohl(tvb, );

  // Check if the packet length is valid
  if (length > ) {
    // Process the packet
    divisor = length / 2;
    process_packet(tvb, pinfo, tree, length, divisor);
  }
}

In the above code snippet, the length variable is fetched from the packet and directly used to calculate the divisor. The length should first be validated to ensure that it is greater than zero before proceeding with further calculations.

Exploit Details

To exploit this vulnerability, an attacker would send a crafted CP2179 packet with a zero-length value to the target system. This will cause Wireshark to attempt dividing by zero, leading to a crash and subsequent denial of service. Wireshark would be unable to process any further packets, disrupting the user's ability to analyze network traffic.

Mitigation

It is highly recommended that users and administrators actively using Wireshark versions 2.. through 4..7 update to the latest version as soon as possible to mitigate the risk posed by CVE-2023-2906. The Wireshark developers have released a security patch that addresses this vulnerability.

The corrected code snippet should look like this

void dissect_cp2179(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
  guint32 length;
  guint32 divisor;

  // Get the packet length
  length = tvb_get_ntohl(tvb, );

  // Check if the packet length is valid
  if (length > 2) {
    // Process the packet
    divisor = length / 2;
    process_packet(tvb, pinfo, tree, length, divisor);
  }
}

In this updated code snippet, the length is now checked to be greater than two (2) before proceeding with the packet processing.

Here are some relevant references for additional information

1. Original CVE Report: CVE-2023-2906
2. Wireshark Security Advisory: WSA-2023-0001
3. Wireshark Download Page: Wireshark Download

Conclusion

CVE-2023-2906 is an important vulnerability to be aware of and address accordingly. Proper validation of packet lengths is crucial for preventing divide by zero errors and subsequent denial of service attacks. To protect your network and ensure its proper operation, make sure to update your Wireshark application to the latest version.

Timeline

Published on: 08/25/2023 21:15:00 UTC
Last modified on: 09/15/2023 22:15:00 UTC